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RESEARCH LIBRARY 
THE GETTY RESEARCH INSTITUTE 


JOHN MOORE ANDREAS COLOR CHEMISTRY LIBRARY FOUNDATION 








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AFAEENTE TREIBHIDE, 


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USES, TESTS FOR PURITY AND PREPARATION 


a 


—On—— 


UHEMIGAL REAGENTS, 


EMPLOYED IN 


QUALITATIVE, QUANTITATIVE, VOLUMETRIC, DOCIMAS- 
TIC, MICROSCOPIC anp PETROGRAPHIC ANALYSIS, 


WITH A SUPPLEMENT ON THE USE OF 


fee ol OT ROSCOPE. 


BYa 


CHAS, OF LURTMAN, M, By 


PROFESSOR OF CHEMISTRY, AND DIRECTOR OF CHEMICAL LABORATORY 


IN THE MISSOURI MEDICAL COLLEGE, 


WITH TWELVE PLATES. 


ST. LOUIS, MO. 
JOHN L, BOLAND BOOK AND STATIONERY CO. 
1890, 








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Entered according to Act of Congress in the year 
ae CHARLES O. CuRTMAN, ~ 
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302 NORTH MAIN STREET, = = 


THE GETTY RESEARCH 
INSTITUTE LIBRARY, 


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GEO G HITCHCOGK 


Piet Vere. 


Having for a number of years been engaged in a variety of 
analytical work, the author has often experienced difficulty in 
readily obtaining some of the rarer reagents, or in procuring 
those which were obtainable in the market, of the necessary de- 
gree of purity. This experience has undoubtedly been shared by 
most practical analysts, and cases of misplaced confidence in 
““chemically pure” reagents have neither been few nor far between. 

So far as the reagents in common use are concerned, there cer- 
tainly has, in late years, been a great improvement, but even now 
itis very difficult to procure, e.g., concentrated sulphuric acid 
completely free from arsenic and from ‘‘nitrose,’’ and absolutely 
pure zinc is very precious, indeed. The practice of testing the 
reagents is as necessary as ever in order to obtain reliable results, 
and a neglect of this precaution in forensic cases would be crimi- 
nal. In the manuals of analytical chemistry modes of testing 
the purity of all reagents in common use are fully described, but 
to find a description of the great number of new reagents intro- 
duced recently into special classes of work, we have to resort to 
journals and monographs, and the information is scattered 
throughout the literature of the day. Even the valuable pamphlet 
of Dr. Krauch, chemist of E. Merck’s celebrated establishment, 
which appeared late in 1888, contains only 116 headings. 

The difficulty of obtaining the desired information at the mo- 
ment of need having been brought home time and again, the 
author was prompted to undertake the laborious task of compil- 
jog all the information to be found in the literature accessible to 
him, and the result is before the reader. The manuscript was 
nearly completed and publication begun in May, 1888, as a serial in 
the Druggist, a monthly issued by the Meyer Brothers Drug Co. As 
but few pages appeared in each number, the completion of the 
printing was considerably delayed. To collect the 400 different 
items treated in book form, electrotype plates were made as each 
number of the journal appeared, and this necessitated the de- 
ferring of any corrections or omissions to a supplement. 

Whenever practicable, the author has endeavored to give 
proper credit to originators of analytical processes, and any omis- 


PREFACE. 


sions which may have occurred are certainly not intentional. 
Out of the vast amount of material before him he has selected 
what appeared to him most important, and in regard to critical 
sifting he has spared no effort. Many of the new reactions were 
thoroughly tested before admitting them, and hundreds of experi- 
ments were made to verify statements in regard to the reliability 
of new methods. 

There being only metric weights and measures referred to in 
the volume, and therefore no possible chance of a mistake, the 
author may perhaps be pardoned the liberty of abbreviating 
gramme by gr. 

As the spectroscope forms so valuable an adjunct to the means 
of analytical research, a short chapter has been added, describ- 
ing the use of the simpler and inexpensive forms usually employed 
in the laboratory, with the aid of the accessories everywhere at 
hand. The descriptions of the spectra give the position of lines 
and bands aecurately by wavelengths, so that they may be con- 
veniently mapped out on diagrams. A number of plates illus- 
trate the text and afford aid in the identification of the spectra. 
As only a limited number could find a place in the short chapter, 
the author has selected of the emission spectra such as may be 
easily produced by the aid of a Bunsen gas burner, or a strong 
alcohol lamp, and of absorption spectra those of the coloring 
constituents of blood and such materials as might be most easily 
mistaken for them, some others referring to the detection of 
adulteration of red wine, or illustrating chemical reactions (e. g. 
furfurol-urea) or identifying color reagents used as indicators in 
volumetric work. 

The author hopes that his colleagues of the craft may find his 
little volume of some use to them, and that they will pass a 
lenient judgment on its short-comings. 


CHAS. O. CURTMAN. 
St. Louris, Mo., March, 1890. 


INTRODUCTION. 


In the succeeding pages the attempt is made to describe the rea- 
gents used in the various processes of analysis. 

The name reagent might be applied to all bodies, simple or com. 
pound, which, when brought together with others, produce, by 
their mutual action upon each other, a change of condition in 
color, odor, state of aggregation, temperature, etc., ete. It is, 
however, usually restricted to those chemicals which we employ 
for the purpose of eliciting information as to the constituents of 
bodies, whose composition we desire to ascertain. The change 
produced by the action of the bodics brought together is called a 
reaction, and is due to a rearrangement of their atoms into new 
molecules. When a certain substance effects such a change only in 
one other, we call it a special reagent for that substance ; when it 
produces a similar effect upon a larger number, it is called a group- 
reagent or general reagent; and as the effect is due to the mutual 
action upon each other, each of the substances may be regarded as 
the reagent for the other. | 

The book is not intended to be a guide to analysis or to compete 
in any way with standard works on that subject, but rather to 
serve as a supplement to them, to aid the analyst in selecting, test- 
ing and preparing the reagents he needs, and to gather into a 
single volume information now scattered over a vast extent of 
chemical literature. 

The arrangement adopted is in most cases to give, first, the USE 
of the reagent; next, TESTs for its purity, and, lastly, such methods 
of PREPARATION as are suitable for ee amaaller quantities for 
use in the laboratory. 

In describing the UsE of reagents the aim has been to give only 
a brief mention of the manifold applications of general reagents, 
and to allude but shortly to the well-known analytical methods 
and conditions under which reactions occur, or the apparatus used, 
- while in the case of those less familiarly known, and used only in 
special processes, reactions, as well as reagents, have been described. 
Space has been given even to some.whose use might have been 
deemed superfluous, as they m wy occasionally prove useful under 
special conditions, 


9 INTRODUCTION. 


The enumeration of Tests for purity includes, in most cases, a 
short description of physical properties, which are often valuable 
helps to identification. Thus, the crystalline form, melting and 
boiling points, specific gravity, solubility at different temperatures 
in water and in other solventsis described. On the other hand, 
such self-evident tests for identity as are to prove that magnesium 
sulphate really contains magnesium and sulphuric acid are gene- 
rally omitted, and only those tests mentioned which are to prove 
freedom from impurities. It is hardly necessary to observe that 
for many purposes absolutely pure reagents are not required, that 
only the absence of certain kinds of impurities may be needed to 
render the reagents serviceable, and that it would entail needless 
trouble and expense to employ pure articles where ordinary com- 
mercial ones suffice. In most cases the tests for absence of all im- 
purities are given and from them only those need to be selected 
which are essential for the special purpose. 

The description of PREPARATION in some eases confines itself to 
modes of purification of commercial articles; in others it gives a 
full outline of the manufacture from the crude material. 

For greater ease of controlling quantitative relations, making 
volumetric solutions, etc., the molecular weights are given with 
most articles, the calculations being based on the table of atomic 
weights on adjoining page. Wherever water, alcohol or acids are 
mentioned without special qualifications, the pure substances, of 
the strength stated in the description of these agents, are intended. 
Thermometric degrees refer to centigrade, boiling points, etc., 
to normal conditicns of 760 millimetres pressure. 

The arrangement of the different articles is according to the al- 
phabetical sequence of the groups, in which the different members 
again follow in alphabetical order. Thus, the first group, acids, 
gives in detail acetic, boric, chromic, ete. The many colur reagents 
and indicators used and proposed, mostly for volumetric processes, 
have been united into a chapter, the individuals of which are ar- 
ranged in alphabetical detail. A general index and another 
giving under the name of each substance the tests described for its 
detection is added at the end of the volume. 


Table of Atomic Weights. 

















7 IL. IL. 
MONADS. | DYADS. TRIADS. 
Li—7.007 Be=9.085 B=10.941 
Na—22.998] Meg—23.959| Al—27.008 
K=—39.019  |Ca—s9.99 Sc—43.98 
(Cu=63.173)| Zn—64.905| Ga—68.854 
Rb=85.251 |Sr—87.874 |Yt—89.816 
(Ag—107.675)| Cd—111.77) In—113.398 
Cs—132.583 . |[Ba—136.768 |La—138.526 
= ds Yb=172.76 
(Au—196.155)} Hg—199.712| T1—203.'715 














| 


Periodic System of Elements. 








| 





H—1. 
IV. V3 
TRIADS and 
TETRADS. | pENTADS. 
C—11.974 N=14.021 
Si—28,195 P—30.958 
Ti—48.” Vd—=51.256 
Ge—72.28| As—74.918 
Zr=-89.367  \Nb—94 
Sn—117.698| Sb—119.955 
Ce—140.424 |Di—146.18 
am Er—165.891! 
ee Ta—182.144 
Pb=206.471 Bi—207.523 
Th=233.414 |— 


Vile VIL. VIII: 
DYADS and |MONADSand 
HEXADS. | HEPTADS. 
O=15.96 F+18.984 
S=31.984 C]l=85.37) ( Fe=55.913 
J Ni—b?. 928 
Cr=52.009 Mn=53.906 } Co==58.887 
| Cu—63.173 
Se=78.797 Br=79.768| ( Ru=101 5 
| Rh=104.055. 
Mo=95.888 |— s Pd—105.737 
Te—=125.. I~126. 557 | Ag—=t07. 675 
Th=148.8 (?) |— 
St: = ( Os=191.12 
Ir=192.651 
= 3 awe | 
Wig a | Pt—=194.415 
Ng=214 —_ Coen 2 155 


Ur=238.482 








. ATOMIC WEIGHTS. 








886°906 | P86'S8T 


TLEISS | cSe'cls 





GB8L°SS8 | F8E Boh 


91V's98 
998° L86 


669 992 
ELB S&S 


SLO 6ETE | 9SF SLOT 


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6881S 96°G86 





989°8EE | G&8 BLP 
99L°LOT | c6L°S6 

60T' LEG | 80% S67 
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884898 


VV6: PLE 
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809° 8LP 
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907 TLE 


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Cre 682 





961 SOT 


066° FIT 
£60°S6T 


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COS" 608 


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666'T6 


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966° S88 


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820908 

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626 C6 


FOE 686 


IT 90L 


699 6LT 
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604° S8T 


966 SP 
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969° 681 


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‘ASO LNANOAYA NI SLHSIYM OINOLVY AWOS AO SATdILTOW 


GEO ¢ HITCHCOCK 


ACIDS. 


ACETIC ACID, H Cz Hs Oz 


UsrEs. ‘Io separate calcium oxalate from phosphate, barium 
chromate from strontium chromate, zinc sulphide from manganese 
and other sulphides, to acidulate solutions, etc. 

U.S. P. acid has specific gravity 1.048, and contains thirty-six 
per cent of absolute acid. Itis generally sold of sufficient purity 
for analysis. 

Tests. It should leave no residue on evaporation (absence of 
non-volatile matters). 

No precipitate should be produced by barium chloride (absence of 
sulphates), nor by silver nitrate (absence of chlorides), nor with am- 
monium oxalate (absence of calcium salts). 

No precipitate should be produced by hydrogen sulphide (absence 
of arsenic and copper groups), nor, after neutralization with am- 
monium hydrate, by ammonium sulphide (absence of iron and 
aluminium groups). 

No bleaching of indigo should occur on heating (absence of nitric 
acid). After neutralization by sodium carbonate, no empyreumatic 
odor nor bleaching of dilute potassium permanganate solution 
should indicate organic impurities. 

PURIFICATION of impure acid may be accomplished by digesting 
it with some potassium permanganate, then adding sodium acetate 
and distilling. 


BORIC OR BORACIC ACID, Hs B Os. 


UsED occasionally instead of borax in assaying and in blow-pipe 
analysis ; also to liberate volatile acids, etc. ; also in the preparation 
of ammonium borofluoride, a reagent for potassium. 

Tests. The colorless, transparent, scaly crystals dissolve with- 
out residue in 26 parts of cold, 3 parts of boiling water, and in 15 
parts of cold alcohol. The watery solution, acidulated with nitric 
acid, should not be precipitated by barium chloride or silver nitrate, 
nor be colored red by potassium sulpho cyanide? When mixed with 
strong sulphuric acid, a crystal of ferrous sulphate should not pro- 
duce a brown, nor a few drops of di-phenylamine a blue color 
(absence of nitrates). Hydrogen sulphide should produce neither 
color nor precipitate in the watery solution, either before or after 


1 


8 ACIDS. 


addition of ammonia to alkaline reaction. Heated on piatinum 
foil, the acid should readily fuse into a glassy, transparent mass. 
PREPARATION. Pure borax is dissolved in twice its weight of pure 
boiling water, one-half its weight of very concentrated hydrochlo- 
ric acid is thoroughly mixed with it, and the liquid set aside to cool 
and crystallize. The crystals are drained on a funnel, washed 
‘with a little very cold, pure water, then redissolved in 5 parts of 
boiling water, and the purified crystals are drained and dried. 


CHROMIC ACID ANHYDRIDE, Cr Os, 


Usrs. Chromic acid is a strong oxidizing agent, but is seldom 
employed in the pure state. A very weak solutionin dilute gly- 
cerin serves to harden tissues for microscopical examination. Itis 
also used to produce with strychnia the characteristic color reac- 
tions; to convert alcohol into aldehyde, etc. 

Tests. The commercial article is of sufficient purity, forming 
long, scarlet, rhombic crystals. 

PREPARATION. Dissolve, by means of heat, two parts of potas- 
sium dichromate in a mixture of seven parts of concentrated sul- 
phuric acid and five parts of water, set aside until the crystals of 
potassium sulphate have separated; pour off the red liquid; add 
eight more parts of concentrated sulphuric acid, and finally drain 
the crystals of chromic acid on a funnel closed with an asbestos 
plug. For most uses potassium dichromate mixed with sulphuric 
acid will answer all purposes, without separating the acid. 


CITRIC ACID, Hs Ce Hs O7 + He O. 


Usrs. Citric acid is occasionally employed instead of acetic acid 
for acidulation in urine analysis, also in the determination of phos- 
phorie acid. 

Tests. The colorless transparent rhombic crystals should leave 
no residue on ignition upon platinum foil. It should dissolve in 
three-fourths of its weight of cool water and in one-half of its 
weight of boiling water. At 15° C., one part should dissolve in 1.15 
parts of 80% alcohol. 0.7 grammes of citrie acid should accurately 
saturate 10 Ce. of normal potassium hydrate solution, phenol phtha- 
lein being used as indicator. 


GALLIC ACID, H C7 Hs Os. 


UsrEs. To show’ the presence of ferrous salts in mineral waters, 
etc., also to indicate the presence of free mineral acids (#lueckiger). 
For this purpose, three parts of ferrous sulphate and two parts of 
gallic acid are each dissolved 1n 100 parts of water and then mixed, 
To this colorless mixture one part of sodium acetate is added, which 


ACIDS. 7 


produces a violet color. When a small quantity of this freshly pre- 
pared mixture is dropped into a liquid containing free mineral acids 
the color is discharged. 


HYDRIODIC ACID, HI. 


Usxs. It serves to recognize some oxygenized ethereal oils, 
which unite with the gaseous acid and may then, by heating with 
alcoholic soda solution, be converted into terpenes. A concentrated 
aqueous solution is used in blow-pipe analysis. 

Tests: The commercial liquid acid is suitable for blow-pipe 
work, even when it has turned brown from partial decomposition. 
The gas for oil analysis must be prepared when needed. 

PREPARATION. Into atubulated retort of 500 Ce. capacity place 
100 Ce. heavy paraffin oil, then 10 grammes white phosphorus ; add 
carefully and gradually 128.2 grammes powdered iodine, and lastly, 
18 Ce. pure water, drop by drop. Heat gently and dry the gas by 
passing over anhydrous phosphoric acid. 


HYDROBROMIC ACID, H Br. 


Uses. Concentrated, pure hydrobromic acid has been recently 
employed as a solvent for mercury, lead and copper, also for lead 
sulphate and especially for metallicsulphides. In conjunction with 
copper amalgam, it converts sulphur, either free or in sulphides, 
into hydrogen sulphide, which may be accurately determined by 
absorption. It is also employed as a delicate test for copper. 

Tests. No residue should be left on evaporation. Barium 
chloride must give no precipitate. On addition of chlorine water 
chloroform shaken up with it should not show the iodine color. 
The precipitate with silver nitrate should be almost insoluble in 
aqua ammonia of U.S. P. strength, and in the ammoniacal filtrate, 
nitric acid should cause only a slight turbidity. 

PREPARATION. Hydrobromic acid of great concentration and 
purity is best made by Harding's method. The vapor of bromine 
is first passed over red hot manganese dioxide to destroy organic 
impurities, then, together with pure hydrogen gas, is passed through 
a tube of platinum containing a layer of finely divided metallic 
platinum (platinized asbestos) heated to a bright red heat. The 
elements unite and the gaseous hydrobromic acid is passed first 
through a tube containing antimony, to absorb free bromine, then 
through a wash bottle, and is finally received into a cool receiver 
containing distilled water. 

Or (according to Squibb) seven parts of pure concentrated sul- 
phuric acid are added to one part of pure water, and, after cool- 
ing, are slowly poured, with constant stirring, into a hot solution 


1* 


8 ACIDS, 


of six parts of pure potassium bromide in six parts of pure water. 
The mixture is set aside for twenty-four hours, the liquidis decanted 
from the crystals of potassium sulphate, transferred to a retort and 
distilled. 

Acid of sufficient purity is now sold by dealers. 


Hydrochloric Acid, H Cl. 


UsED as a general solvent; also to detect lead, silver, mercurous 
salts and free ammonia, to acidulate, to liberate boracic and other 
acids. 

Tests. Colorless liquid leaving no residue on evaporation. 

Must not color a mixture of starch and potassium iodide (absence 
of chlorine and of ferric chloride). 

Must not bleach blue iodized starch in dilution (absence of sul- 
phurous acid). 

No precipitate should be produced by barium chloride (absence 
of sulphates), nor by hydrogen sulphide (absence of arsenic and 
copper groups and sulphurous acid), nor, after neutralizing with 
ammonia, by ammonium sulphide (absence of iron and aluminium 
groups). 

It should leave chloroform colorless, even after addition of 
chlorine water (absence of iodine, bromine). 

When hydrochloric acid is to be used for arsenic testing, its per- 
fect freedom from even traces of arsenic must be proven by placing 
about 2Ce of the acid, diluted with an equal amount of water, into 
a test tube, adding a little pure granulated zinc, and covering the 
mouth of the test tube with a piece of filter paper, moistened with a 
drop of silver nitrate solution; or inserting a slip of the paper with 
the silver solution into a slit of a loosely fitting cork, so as to hang 
into the test tube without coming in contact with its sides. 

Hydrogen gas will be evolved, which, if arsenic be present, will 
contain arsenetted hydrogen and blacken the silver spot on the paper. 
If sulphur dioxide be present, blackening will also occur through 
its reduction and formation of hydrogen sulphide. A paper moist- 
ened with lead acetate will be blackened by sulphur, but not by 
arsenic. 

To purtfy crude hydrochloric acid, which generally contains 
arsenic, one litre of it is mixed with 10Cce. of concentrated stannous 
chloride solution (or four grammes of finely granulated tin), and 
permitted to stand for twenty-four hours, after which time a few 
drops of the clear acid must show a slight excess of stannous 
chloride, by producing a precipitate in a solution of mercuric 
chloride. The acid is then separated from the precipitate, placed 


ACIDS. 9 


into aretort and, after adding twenty-five grammes of sodium 
chloride, distilled into a receiver containing 500Cc. of pure water, 
until most of the acid has passed over. As perfectly pure acid may 
be obtained cheaply and readily, it will rarely be advantageous to 
purify the crude on a small scale. 

Hydrochloric acid of U.S. P. strength has specific gravity 1.16; 
contains 31.9 per centof HCl, and is suitable for analytical purposes. 

For volumetric analysis, normal hydrochloric acid, containing 36.37 
grammes of HCl in one litre, is made by diluting the strong acid 
carefully until it accurately neutralizes an equal volume of normal 
alkali solution. 

A most accurate standard solution, by which the whole series of 
normal alkali and acid solutions may be adjusted, is obtained by 
titration with deci-normal solution of silver nitrate. 


HYDROFLUORIC ACID, HF. 


UsrEp to decompose minerals containing borates and silicates 
either in form of gas or in watery solution. 

Tests. Liquid hydrofluoric acid, as supplied by dealers in gutta 
percha bottles, is generally pure, but if made from impure fluor- 
spar may contain hydro-fluo-silicic acid, and should, therefore, be 
tested by evaporation on platinum foil, when no residue should be 
left ; also by saturation with pure potassium hydrate,when it should 
yield no precipitate of potassium silico fluoride. 

PREPARATION. As the apparatus for making the liquid acid in 
quantity is somewhat expensive, it will generally be best to buy 
from dealers and test for purity. Whensmall quantites are needed, 
either in gas or liquid form, a cylindrical leaden vessel with lid may 
be employed, of sufficient size tosupport on a tallleaden tripod the 
platinum crucible or dish, which is to contain the water to absorb 
the gas, when liquid acid is wanted, or to contain in fine powder 
the mineral to be decomposed by the acid gas. 

On the bottom of the leaden vessel a mixture of two parts of 
powdered kryolite, with five parts of concentrated pure sulphuric 
acid, is spread ; the tripod is placed in position, and on it the plat- 
inum vessel; the lid is loosely laid on, and gentle heat is employed 
to evolve the gas from the mixture. When fiuorspar has to be 
used instead of kryolite, the first portion of the gas must be suffered 
to escape before the platinum Vessel is put on the tripod, so as to 
get rid of the silicium tetrafluoride liable to form from silicates, 
which often occur in commercial fluorspar. Great care should be 
taken to avoid inhaling the gas or to prevent the liquid from coming 
in contact with the skin 


10 ACIDS. 
HYDROFLUOSILICIC ACID, Hz Si Fe. 


Usrep to separate barium from strontium, and occasionally to 
detect potassium. Also in micro-petrographice work. 

Tests. It must give no precipitate with strontium sulphate solu- 
tion. It must leave no crystalline residue on evaporation. 

PREPARATION. Into a flask of half a litre capacity there isin 
troduced a mixture of twenty-five grammes each of fine quartzsand 
and powdered pure fluor spar or kryolite, with 125 Ce. of pure concen- 
trated sulphuric acid. The flask is closed by a cork, through which 
a wide glass tube passes, bent twice at right angles, whose free end 
dips into a beaker containing half a litre of pure water. When the 
flask is gently heated, silicon tetrafluoride gas is evolved, which in 
contact with the water is at once decomposed according to the fol- 


lowing equation: 
3SiF4+38H2O = 2HeSik's+ HeSi0s. 


The gelatinous silica thus formed surrounds each gas bubble as 
it enters the water, and necessitates continual stirring to prevent 
the formation of channels through which the gas can escape unde- 
composed, or the clogging of the delivery tube. Itis best to either 
enlarge the end of the delivery tube by attaching thereto a small 
funnel tube, or else to pour some mercury into the beaker, just suf- 
ficient to let the end of the delivery tube reach under its surface. 
When gas is no longer evolved, the gelatinous mixture of silica and 
hydrofluosilic acid is separated by filtration, first through a clean 
linen strainer, then through filter paper, and the acid is preserved 
insmall glass stoppered vials in acool place. As the glass flask is 
corroded, so as to be unfit for subsequent use, it is best to make a 
full supply of acid at once. 


HYDROSULPHURIC ACID, H:S. 


Hydrogen Sulphide or Sulphuretied Hgdrogen. 


UsED as a general reagent to separate metals into groups, and to 
identify some by the characteristic color of their sulphides. 

It is either used by passing the gas directly into the metallie solu- 
tions, or by adding to them a saturated solution of HeS in pure 
water. 

Tests. Water saturated with pure HzS leaves no residue on 
evaporation, does not forma precipitate on addition of ammonia, 
gives acopious precipitate of sulphur on addition of ferric chloride, 
and must have the strong characteristic odor of the gas in full 
strength. 


ACIDS. ll 


To insure purity, it is best to use in its preparation only pure in- 
gredients, and to pass the gas through a suitable wash bottle to 
deposit impurities mechanically carried over from the apparatus. 

PREPARATION. Ferrous sulphide is treated in a suitable appar- 
atus with pure dilute sulphuric or hydrochlorie acid. 

To obtain good ferrous sulphide, put cuttings of clean sheet iron 
or nails into a hessian crucible, heat to a full white heat, then add 
pure sulphur in small lumps until the mass is fused, and pour 
into a suitable clean mould. | 

Many varieties of apparatus have been devised for making sul- 
phuretted hydrogen. A very simple one may be constructed by 
taking astout wide mouth bottle, perforating its cork twice, passing 
through one of the perforations a funnel tube reaching nearly to 
the bottom, through the other a glass tube bent twice at right 
angles, whose short end just reaches through the cork, while the 
longer passes through the cork of a smaller wide mouth bottle, 
under the surface of the water with which it is about half filled ; while 
another tube, also bent twice at right angles, rises from above the 
water to conduct the washed gas into the receiving vessel, which is 
nearly filled with pure, cold water. Into the larger bottle a suffi- 
cient quantity of ferrous sulphide, broken into small lumps, is placed 
and the dilute acid poured in through the funnel tube. All joints 
must be perfectly tight. 

To ascertain whether the water is saturated with the gas, close 
the bottle and shake it well. Ifthe water still absorbs a portion of 
the gas enclosed, a vacuum will result, indicated by an inward rush 
of air on reopening the bottle. Before sealing the small bottles, in 
which the solution is to be preserved, displace the air above the 
liquid with hydrogen sulphide. 


IODIC ACID HI Os, and IODINE PENTOXIDE Iz Os. 


Usrs. Iodic acid is used in analysis of alkaloids (e. g. to dis- 
tinguish morphine from codeine). It is sometime kept as anhy- 
dride, iodine pentoxide, Iz Os, and dissolved when needed, or else it 
is made for immediate use by mixing potassium iodate with sul- 
phuric acid. 

Tests. The anhydride, Iz Os, is a white crystalline powder, which 
at 800° C. is decomposed into iodine and oxygen, leaving no residue. 
It is easily soluble in water, forming iodic acid. Its solution must 
not color starch solution. 

PREPARATION. JDissolveiodine in very concentrated nitric acid. 
Eyaporate to dryness, so as to volatilize any surplus, of either acid 
or iodine, not exceeding a temperature of 200° C. Dissolve the yel- 
low residue in water. Evaporate again to dryness, and then keep 


12 ACIDS. 


the residue at 200°C. until the color has become white. The pen- 
toxide thus formed is dissolved in ten parts of distilled water, as it 
is needed. 


META-DIAMIDO-BENZOIC ACID, H Cz Hz Ne O2 + He O. 


Usrs. With nitrous acid it is colored intensely yellow, and forms, 
when dissolved in sulphuric acid, a most delicate reagent for traces 


of nitrites. (Griess.) 

Tests. The long needle-shaped crystals are sold of sufficient 
purity. ; 

PREPARATION. As the solution decomposes by long standing, 
only enough may be prepared for present use by dissolving one part 
in about 100 parts of very dilute sulphuric acid. 


META-TUNGSTIC ACID, He Ws O13 + 8 He 0. 
Meta-Wolframic Acid. 


Usses. Scheibler recommended the use of the free acid and of the 
sodium salt, as well as the phospho-wolframic acid (see under phos- 
phoric acid) for analysis of alkaloids, some of which it precipitates, 
but offers no advantage over other reagents. It is sold of sufficient 
purity by dealers. 


MOLYBDIC ACID, H2 Mo Ou. 


AND DERIVATIVES. 

Molvbdic acidand its sodium and ammonium salts are now supplied 
in commerce perfectly pure, and at such rates that their prepara- 
tion and purification from the crude mineral is not advantageous. 

a. SODIUM PHOSPHOMOLYBDATE, Naz POs 10Mo Og (also 
11 and 12 Mo Os) in nitric acid solution. 


De Vry’s or Sonnenschein’s Reagent. 


Usts. Produces in solutions of ammonium salts and alkaloids 


yellow precipitates. 

PREPARATION. Dissolve 1.5 grammes sodium molybdate and 
0.86 grammes sodium phosphate in 14 Cc. boiling water, then add 
nitric acid, of spec. gr. 1.42, sufficient for 16 Ce. Preserve in closely 
stopped vials, to prevent contact with ammoniacal vapor. 


b. SULPHO-MOLYBDIC ACID, on MOLYBDENYL SULPHATE, 
Mo O2S0Os. 
Froehde’s Reagent. 
Usrs. Produces characteristic colors with morphine, codeine, 
narcotine, etc. 


ACIDS 13 


PREPARATION. Immediately before using dissolve in 1 Cc. conc. 
pure sulphuric acid about 5 milligr. of molybdic acid or 5.5 mgr. 
of sodium molybdate. 


ec. AMMONIUM MOLYBDATE solution in nitric acid (NH4)e 
Mo O,. 

UsED for precipitation of phosphoric acid. 

PREPARATION. Dissolve one gramme finely powdered ammonium 
molybdate in 6.7 Ce. of hot water (if the salt has lost ammonia by 
long keeping, a little ammonia water must be added), and pour this 
solution into 6.7 Cc. of pure nitric acid of spec. gr. 1.2 (made by mix- 

‘ing 3.3 Ce. of pure nitric acid of spec. gr. 1.42 with 3.4 Ce. of dis- 
tilled water). It does not answer so well to pour the acid into the 
aqueous solution. Preserve inthe dark. 

For washing precipitates, one volume of this solution is diluted 
with three vol. of pure water. 


Note. In most cases it is not advantageous to prepare this salt 
on a small scale from the ore. Where, however, either molybdenite, 
MoS8s, or molybdenum ochre, Mo Os, or lead molybdate, Pb Mo Ou, can 
be obtained cheaply, the pure acid or the ammonium salt may be 
prepared as follows: 


Lead molybdate is finely powdered, and then digested for some 
days with very dilute hydrochloric acid to remove carbonates 
accompanying it. The powder is separated and boiled with con- 
centrated hydrochloric acid. After cooling, the solution of molyb- 
dic acid is decanted from the lead chloride, a small amount of sul. 
phuric acid is added to precipitate most of the remaining lead, the 
liquid is filtered through asbestos, and, after addition of some nitric 
acid, is evaporated to dryness. The product is impure molybdic 
acid, and it must be purified in the same manner as the native im- 
pure acid occurring as molybdenum ochre. The finely powdered 
substance is digested at a temperature of about 20° to 25° C. with 
ammonia water, being frequently stirred. When the acid has been 
dissolved, asmall amount of ammonium sulphide is added to precipi- 
tate lead, ete. Itis then filtered, concentrated by evaporation, and 
set aside to crystallize. The crystals are purified by recrystalliza- 
tion. When molybdenite (molybdenum glance) is used, it is finely 
powdered, mixed with pure sand and roasted in a muffle, scorifier or 
platinum dish. To oxidize fully, the mixture must be frequently 
stirred, so as to expose it freely to access of air while heated to a 
red heat. Sulphur is volatilized as SO, while molybdie acid is 
formed, which, when finished, will appear lemon yellow while hot, 
but white when cooled. It is treated for purification like the im- 
pure acid obtained from other ores. 


14 ACIDS. 


NITRIC ACID, H N Os, 


UsED as a solvent of silver, mercury and other metals, as an ox- 
idizer of ferrous and other salts, and to detect bile colors, uric acid» 
brucine and other alkaloids by characteristic color reactions. 

Tests. It should be colorless, leave no residue on evaporation, 
give, when diluted, no precipitate with silver nitrate (abs. of chlor- 
ine), nor with barium nitrate (absence of sulphate). 

After neutralization it must not give a precipitate with hydrogen 
sulphide or ammonium sulphide (abs. of metals). 

It must show absence of arsenic by Fleitmann’s test, i. e., on add- 
ing potassium hydrate in considerable excess of neutralization and 
boiling the mixture with pure zine or aluminium, the gas evolved 
must not blacken paper moistened with silver nitrate solution. 

After dilution it must not color starch solution blue or chloroform 
violet, even after adding a little hydrogen sulphide or sulphurous 
acid (abs. of iodides and iodates). 

PREPARATION. To commercial nitric acid a solution of silver ni- 
trate is added as long asa precipitate falls, and then in slight ex- 
cess. The clear liquid is decanted from the precipitate and care- 
fully distilled, leaving a small residue in the retort. Pure nitric 
acid of the U.S. P. strength, spec. gr. 1.42, is needed for bile tests. 
For most other purposes, mix equal volumes of the strong acid and 
distilled water, or obtain pure acid of spec. grav. 1.2. The strong 
acid is easily decomposed by light, and then contains nitrogen tet- 
roxide and lower oxides, and becomes yellow. 

Red Fuming Nitric Acidis a concentrated nitric acid charged 
with nitrogen tetroxide, and may be prepared by placing a mix- 
ture of 100 grammes of potassium nitrate (absolutely free from 
chloride) and 1.5 grammes starch into a tubulated retort of 1 litre 
capacity, connecting with a suitable refrigerator, and adding a 
mixture of fifty grammes each of pure concentrated sulphuric acid 
and pure fuming sulphuric acid. The distillate may be received 
separately, or, if not needed of such concentration, into a receiver 
containing 100 Cc. of pure concentrated nitric acid. At first the 
heat evolved by the mixture is sufficient, afterwards a goons heat 
may be applied to finish the distillation. 

A much simpler mode will furnish an acid of less purity, ie use- 
ful for some purposes. Nitrogen dioxide is evolved from a flask 
containing copper chipsand nitric acid, the gas is passed first into a 
washbottle filled partly with nitric acid, so as to convert it into tetrox- 
ide, and from thence into the receiver. In this strong nitric acid is 
contained, which is gradually saturated with the gas. 

Sometimes pure sulphuric acid is thus saturated with nitrogen 
tetroxide and used in the analysis of iodides. 


ACIDS. 15 


Concentrated red fuming nitric acid is used to oxidize sulphur 
into sulphuric acid and sulphides into sulphates, also to liberate 
iodine from iodides. 

Normal Nitric Acid is occasionally used for alkalimetric deter- 
mination of the hydrates and carbonates of alkaline earths. It is 
prepared by diluting a stronger acid with pure water until it cor- 
responds in strength with a normal alkali solution. It contains 
62.91 grammes of HNOs in one litre. 


NITRO-HYDROCHLORIC ACID. 
Nitro-Muriatic Acid or Aqua Regia. 


Usgp as a solvent of gold, platinum, etc., to decompose mercuric 
and other sulphides, and as a source of chlorine. 

PREPARED by mixing one volume of nitric acid of spec. grav. 1.42 
with 3.3 vol. hydrochloric acid of spec. grav. 1.16. 

Nitroxyl chloride, NO2Cl, nitrosyl chloride, NOCI, and free chlor- 
ine are formed: 


2HN0Os+4HClI=NOsCl+NOC1+Clh+3 H20. 


The mixture must be keptcool. After effervescence has ceased 
the acid is preserved in a cool place, in small vials, not entirely 
filled. 

OSMIC ACID ANHYDRIDE, Os 0.. 


Osmium Tetroxide; Perosmic Acid. 


Usss. It liberates iodine from iodides. A 1% solutionis used in 
microscopical work to stain nerve fibres black, and thus differen 
tiate them from surrounding tissues. 

The commercial article is of sufficient purity. It is very poison- 
ous, and should be handled with extreme caution. 


OXALIC ACID, Hz C2 O. + 2H2 0. 


UsgEs. In qualitative analysis the free acid is but rarely employed 
for precipitation of calcium salts, etc.; for microchemical work so- 
lutions of various strengths are inuse. A normal volumetric solu- 
tion is used in alkalimetry, and a deci-normal one as a companion to 
deci-normal solution of potassium permanganate. 

Tests. Oxalic acid forms colorless, transparent, clinorhombic 
prisms, soluble in 14 parts of water at 15°C. On exposure to dry, 
warm air it loses water of crystallization and forms a white powder. 
On being heated on platinum foil, it should completely volatilize 
without emitting odor of burnt sugar, or leaving any residue. It 
should not blacken by heating with concentrated sulphuric acid. 
A cold, saturated solution in water should not become turbid by 
mixing with an equal volume of cold alcohol. 


16 ACIDS. 


PREPARATION. To obtain pure oxalic acid from the crude com- 
mercial article, 1 part of crude acid is dissolved in 10 parts of dis- 
tilled water at 15°C. This leaves a considerable quantity undis- 
solved, among which are most of the impurities. The saturated 
solution is filtered off, concentrated to three-fourths of its volume 
and set aside to crystallize. Thealkaline oxalates yet present erys- 
tallize with this first portion. The motherlye, which now contains 
only pure oxalic acid, is carefully decanted, concentrated and left 
to crystallize, being occasionally stirred to prevent the formation of 
large crystals which might enclose moisture. Thecrystals are now 
drained on a funnel, and lastly dried on blotting paper. Thus puri- 
fied, the acid contains two molecules of water, which it retains un- 
changed so long as it is kept in close bottles at ordinary tempera- 
tures, so that its composition may be strictly relied upon for quan- 
titative work. 

Normal Solution of Oxalic Acid 
is obtained by dissolving 62.86 grammes (63) of carefully selected 
crystals of HeCe Os + 2He O in distilled water, so as to make 1 litre. 
Control by testing with normal alxali solution. Deci-normal solu- 
ticn is made by appropriate dilution. 
PERCHLORIC ACIS, H Cl 0:+ 2H20, 


Uses. From solutions of potassium salts it precipitates potas- 
sium perchlorate, 1 part of which at 15°C. is soluble in 70 parts of 
water, insoluble in alcohol. The crystals are rhombic and are of 
importance in microscopic determination of potassium. It is also 
a special reagent (/raude’s) for aspidospermine, which it colors in- 
tensely red, while strychnine is colored a reddish yellow and bru- 
cine a dark brownish yellow; other alkaloids give no reaction. 

Tests. Pure, anhydrous perchloric acid is a colorless liquid, 
fuming in air, spec. grav. 1,782, very corrosive. It cannot be pre- 
served in this state many days, as it decomposes, becomes colored 
and spontaneously explodes. When united with 2 molecules of 
water the acid may be safely preserved, and forms a syrupy liquid, 
boiling at 203°C. The somewhat more dilute article furnished by 
dealers in chemicals is of sufficient purity. 

PREPARATION. Pure potassium chlorate is carefully heated to 
about 400°C., when after fusing to a thin liquid it loses a portion of 
its oxygen and becomes thick. It is now removed from the fire, 
the KCl extracted by cold water, and then recrystallized from a 
saturated boiling solution, when KCl Os, deposits first in small 
rhombic crystals. These are dried and 1 part mixed with 4 parts of 
cone. sulphuric acid and distilled. The distillate is purified by re- 
distillation at 110°C., and 5 parts of it are diluted with 2 parts of 
distilled water. 


ACIDS, 17 


PHOSPHORIC ACID AND DERIVATIVES. 


a, ORTHO-PHOSPHORIC ACID, HsP Os,. 
Tribasic Phosphoric Acid. 


UsEpD occasionally to set free volatile acids from their salts (as 
acetic acid from calcium acetate) so as to separate them by distilla- 
tion without admixture with another volatile acid; also in testing 
for alkaloids it colors aconitine and digitalin violet; also to pre- 
pare compound phosphoric acids (phospho-molybdic, phospho- 
wolframic, etc.) The anhydride, P2Os, is used for dehydration. 
For most purposes the U.S. P. solution, containing 50 per cent of 
Hs P Ou, of sp. gr. 1.847, may be used. 

Tests. The absence of arsenic must be provenin similar manner 
asin hydrochloric or nitric acid, potassium permanganate solution 
having first been added drop by drop until no longer decolorized, 
so as to oxidize any phosphorous acid present. Silver nitrate should 
produce no precipitate in phosphoric acid diluted with 5 parts of 
water. A brown or black precipitate would indicate phosphorous 
acid; a white, hydrochloric. 

Indigo solution must not lose its color by heating with diluted 
phosphoric acid, nor should a cooled mixture of solution of ferrous 
sulphate with concentrated sulphuric acid show adark color at the 
zone of contact when phosphoric acid is carefully poured upon it 
(absence of nitric acid). 

Hydrogen sulphide must produce no precipitate in diluted phos- 
phorie acid saturated with the gas, even after standing for ten or 
twelve hours. Neither albumen nor barium chloride should pro- 
duce a precipitate (absence of sulphuric and of metaphosphoric 
acids). 

b. METAPHOSPHORIC ACID, HP Os. 


Usss. To detect albumen, with which it forms a white precipi- 
tate. For use in urine analysis, a solution of 1 part of glacial phos- 
phorie acid in 10 parts of water and 1 part of acetic acid is recom- 
mended. In blow-pipe work the free acid is now rarely used, the 
sodium salt obtained from microcosmic salt being preferred. 

The commercial glacial phosphoric acid is sufficiently pure for 
these purposes. 


c. PHOSPHO-ANTIMONIC ACID. 
Schulze’s Reagent. 


UseEp but rarely as a general precipitant of alkaloids, being less 
delicate than sodium phospho-molybdate (see molybdic acid, etc.), 


18 . ACIDS. 


except with atropine. Brucine is precipitated with rosered color, 
dissolved by heating ; other alkaloids and ammonia white; caffeine 
is not precipitated. 

PREPARED by adding 1 Cc. antimonic pentachloride (obtained by 
heating pure powdered antimony in a rapid current of chlorine 
gas) to a mixture of 1 Ce. pure, 50 per cent phosphoric acid with 2 
Ce. of water; or 1 Ce. antimonic chloride with 8 Ce. of a saturated 
solution of sodium phosphate, and decanting from any precipitate 
which may have formed after standing. 


d. PHOSPHO-TUNGSTIC or PHOSPHO-WOLFRAMIC ACID. 
Scheibler’s Reagent. 


UsED, like the preceding, for precipitation of alkaloids, but does 
not offer any advantages over phospho-molybdic acid or sodium 
meta-wolframate (meta-tungstate ). 

PREPARED by dissolving 1 gramme sodium tungstate, NaioWi2 Ou 
+ 28H O, in 10 Ce. water, and adding 1Cc. pure phosphoric acid 
of U.S. P. strength. 


PICRIC ACID, Ce H2(NOz)s OH. 


Carbazotic Acid, or Tri-Nitro-Phenol. 


UseED in detection of albumen, glucose and alkaloids. 

The commercial article is sufficiently pure when in distinct crys- 
tals. 

PREPARATION. As picric acid is liable to explode when suddenly 
heated it should be prepared with great caution. Nine parts of 
crystallized phenol are dissolved in 10 parts concentrated sulphuric 
acid, so as to form phenol sulphonic acid. To this there are gradu- 
ally added 45 parts of nitric acid of specific gravity 1.42, previously 
diluted with 20 parts >f water. At the end of the reaction the mix- 
ture is carefully neutralized with potassium carbonate. The po- 
tassium picrate (requiring 340 parts of water for solution of 1 part) 
precipitates. The precipitate is separated and purified by recrys- 
tallization from boiling water. At last, dilute sulphuric acid is 
added, so as to liberate the picric acid; the crystals are separated, 
washed with a little water and recrystallized for purification, if 
necessary. 

For use, 1 centigramme is dissolved in 10 Ce. hot distilled water, 
and, if necessary, filtered after cooling. 


PYROGALLIC ACID, Ce Hs(OH)s. 


Pyrogallol. 


UseED in alkaline solution to absorb oxygen; with sulphuric acid 
to detect minimal quantities of nitric and nitrous acid, e. g., in 


ACIDS. 19 


drinking water. Also to detect glycerin by boiling the liquid with 
a few crystals of pyrogallic acid and some sulphuric acid, then di- 
luting and adding stannic chloride, when the presence of glycerin 
is indicated by a reddish violet color (Reichl). 

The white crystals of the commercial article are sufficiently pure. 


ROSOLIC ACID, CaHisOz, and AURIN or PARAROSOLIC ACID, 
Cig His Os, 


as well as the yellow corallin, which contains them, are used as indi- 
cators in alkalimetry, especially for free ammonia. It also suits 
well for all mineral acids and oxalic, but not so well for other or- 
ganic acids. 1 gramme is dissolved in 100 Ce. very dilute alcohol. 
The solution turns violet-red with alkalies, yellow with acids. 


SALICYLIC ACID, H Cz Hs Ox. 


This acid is rarely used as areagent. Flueckiger proposes it to 
detect oil of peppermint, which, with the fused acid, is colored bluish- 
green. If alcohol be added the solution becomes dichroic, blue 
with transmitted, red with reflected light. The commercial article 
is sufficiently pure for this purpose. 


SILICIC ACID, H2Si Os. 


Usss. Silicic acid, as well as silicon dioxide, Si O2, is occasionally 
used as a fluxin blowpipe work. The precipitate obtained in making 
hydro-fluo-silicie acid, when sufficiently washed and dried, consists 
of pure acid. 


SILICO-TUNGSTIC ACID, Hs Wi2Si O12 + 29 H20. 
Godeffroy’s Reagent. 


UsED as a very delicate reagent for the precipitation of alkaloids 
from dilute solutions. 

PREPARATION. Boil 60 parts of crystals of commercial sodium 
tungstate, Nai Wie Oa + 28 He O, with 1 part of freshly preci) ita- 
ted silicic acid, for about an hour, with 200 parts of water. Filter; 
heat the filtrate again to boiling, and add a slight excess of freshly 
prepared mercurous nitrate solution. Mercurous silico-tungstate 
precipitates, which is washed on a filter, and then decomposed with 
a sufficient amount of hydrochloric acid to decompose the salt. 
Mercurous chloride remains as a residue, and the filtrate on evapo- 
ration forms transparent, yellowish, quadratic, octohedral crystals, 
of the composition Hs Wi2Si O2-+ 29 HzO. One part of these is 
dissolved for use in 10 parts of distilled water. 

A less pure acid may be obtained more readily by omitting the 
precipitation by mercurous nitrate and decomposing the solution 
of sodium silico-tungstate directly with hydrochloric acid. 


20 ACIDS. 


SULPHANILIC ACID, NHe2 C Hs SOs H + 2H: O. 
Aniline-Para-Sulphonic Acid. 


UsED in conjunction with naphthylamine sulphate to detect small 
amounts of nitrites by the production of an intense red color 


(Griess). Itis converted by addition of nitrous acid into 
Di-azo-benzol-sulphonic acid, or Benzol-sulphon-diazide, 


which 1s employed to produce LHhrlich’s Diazo-reaction in urine. 
Also as a delicate test for bilirubin, and, in connection with sodium 
amalgam, to detect aldehydes. The test solution for urine and 
bilirubin is made as follows: 12 to15 Cc. of nitric or hydro- 
chloric acid are diluted to 350 Cc. with pure water, and then 
saturated withsulphanilic acid. Just before using, 5 Ce. of a solution 
of 1 part of sodium nitrite in 200 parts of water are added. Equal 
parts of this mixture and the urine are then mixed with a few drops 
of ammonia water. After standing for some hours, normal urine 
shows a deeper yellow or orange color, which, however, is not in- 
tense enough to stain the foam. The deposited earthy salts are not 
colored. In the urine of typhoid fever, measles and phthisis, a char- 
acteristic red color is developed, plainly visible in the foam, while 
the deposit of earthy salts assumes a green to violet color. 

To detect bilirubin, urine is mixed with equal volumes of dilute 
acetic acid (6 percent) and the reagent. If turbidity renders it 
necessary, strong acetic acid may be used in addition. A violet- 
red color shows the presence of bilirubin. Orthe urine is shaken 
with chloroform, which dissolves the bilirubin. The chloroform 
solution is removed and mixed with about double its volume of the 
reagent, and enough alcohol added to make a clear solution. At 
first a yellow color appears, quickly changing to red. If now 
strong hydrochloric acid is added, the color changes through violet 
and purple tints to a pure blue, which remains for some time. 
Addition of sodium hydrate changes the blue to a greenish and red 
color. 

It is also used in connection with sodium amalgam to detect 
aldehydes. With these ared color is produced, changing to violet 
(Fischer and Penzold). It is prepared by dissolving 2 parts of sulph- 
anilic acid in about 15 parts of normal sodium hydrate, adding 1 
part of sodium nitrite and pouring the solution into 20 parts of 
cold normal sulphuric acid. Small needle-shaped crystals precipi- 
tate, which must be dried on filter paper and preserved in a cool 
place, as a temperature of 60° C. causes them to decompose. When 
mixed with ammonia, they violently explode. 

Tests. The acid forms colorless, rhombic prisms, which easily 
lose water of crystallization; it is soluble in 182 parts of cold water. 


ACIDS, 21) 


It is obtained of sufficient purity from dealers or by preparing it 
according to the following directions: 

PREPARATION. On the small scale, sulphanilic acid may be pre- 
pared by heating 1 part of pure aniline oil with 2 parts of fuming 
sulphuric acid, and purifying the product by repeated recrystalliza- 
tion. 

Also by decomposing commercial Helianthin, called also Orange 
III, and consisting of sulpho-dimethyl-amido-azo-benzol, (CHs)eN. 
Ce Hs. N:N.CgH4.SO03H, by a reducing agent into sulphanilic acid 
and para-amido-dimethyl-aniline. As the latter is used as a most 
delicate reagent for hydrogen sulphide, a process for the prepara- 
tion of both is here given. 

One part of helianthin is triturated with five parts of water and 2 
parts of freshly prepared ammonium sulphide, and heated ona 
water bath. Sulphanilic acid and para-amido-di-methyl-aniline are 
formed, the first of which is insoluble in ether, the latter soluble, 
The solution is therefore shaken with ether, left to stand a little 
while, and the ethereal layer separated; the operation being several 
times repeated, so as to use an amount of ether about equal in bulk 
to the solution. The united ethereal layers are digested with white 
lead to remove ammonium sulphide, filtered and mixed with con- 
centrated sulphuric acid, previously dissolved in an equal bulk of 
ether. The mixture is set aside to form crystals of sulphate of para- 
amido-dimethyl-aniline, which is preserved as a reagent for HS. 
After removal of the ethereal solutions, the residue containing the 
sulphanilic acid is heated to boiling to remove ammonium sulphide 
and set aside to deposit the acid, which may be purified by recrys- 
tallization. 


SULPHURIC ACID, Hz SO: 


Uses. Sulphuric acid is used in a variety of chemical operations. 
For some, the crude oil of vitriol of commerce suffices, as for drying, 
etc.; for others, the pure acid, either in concentrated or dilute state, 
is employed. Among its applications are: neutralizing alkalies; 
liberating nitric, hydrochloric, boric, phosphoric and other acids 
from their salts ; recognition of oxalic and other organic acids by 
their decomposition products ; evolution of hydrogen, hydrogen 
sulphide, arsenetted hydrogen and other gases ; detection of lead, 
barium and strontium, etc. 

A small amount of nitric acid in concentrated sulphuric acid is 
used as Hrdmann’s Reagent in the analysis of alkaloids, and is pre- 
pared as follows: 1 drop of nitric acid of spec. grav. 1.25 is dissolved 
in 16 Ce. water. Of this solution 10 drops are added to 20 grammes 
pure concentrated sulphuric acid. 


2 


22 ACIDS. 


The concentrated commercial acid (oi! of vitriol) is, on account of 
its manufacture from pyrites, so often contaminated with arsenic 
that for most purposes of analysis it is best to buy the pure acid, 
which is now made on the large scale, in platinum stills, so cheaply 
that it is not profitable to incur the trouble and risk of preparing it 
by redistilling the crude acid from glass on a small scale. 

Tests. Pure concentrated sulphuric acid should contain at least 
96 per cent of He SO4 and have sp. gr. 1.810. It should be colorless, 
and must be protected from dust and moisture in well closed, glass- 
stoppered bottles. 

It must show absence of the nitrogen acids by leaving colorless at 
the zone of contact with the cone. sulphuric acid dilute solutions of 
ferrous sulphate, brucine, di-phenyl-amine, meta-phenylen-diamine, 
para-toluidine or pyrogallic acid. It must, after dilution with much 
water, not color blue a dilute solution of potassium iodide and 
starch (nitrous acid). 


To show absence of arsenic and of sulphurous acid place 5 Cc. of 
diluted acid into a test tube, add a few granules of pure zine, and 
cover the test tube with a cap of filtering paper, moistened with 
a drop of silver nitrate. Blackening of the silver indicates arsenic 
or sulphurous acid. If lead acetate be used instead of silver nitrate 
to moisten the paper, blackening occurs only if sulphurous acid is 
present, which is reduced to hydrogen sulphide by the nascent 
hydrogen. 

Absence of lead is shown by carefully pouring upon a few Ce. of 
sulphuric acid in a test tube some hydrochloric acid. A white tur- 
pidity at the zone of contact shows the presence of lead, while pure 
acid remains clear. The sulphuric acid remaining clear when 
mixed with about 4 volumes of pure alcohol indicates the absence ~ 
of lead, lime and iron. 

Selenous acid is shown by a red precipitate of selenium, when 
sulphurous and hydrochloric acids are added in small quantity. 

On saturation with ammonia and ignition on platinum foil no 
residue should remain. 

PREPARATION. When it becomes necessary to purify commercial 
acid in the laboratory, the nitrogen compounds are first removed 
by mixing in a large porcelain dish 1 litre of the acid with about 6 
grammes of ammonium sulphate and heating the mixture until 
copious white vapors of acid arise. 

To remove arsenic it is necessary to convert its trioxide, which 
easily volatilizes at the boiling point of the acid, into pentoxide, 
which does not pass over with the sulphuric acid during distillation. 
Hence, before the acid has fully cooled, 10 grammes of manganese 
dioxide are added, and the mixture heated to the boiling point. 


ACIDS. 23 


After cooling. the clear liquid is separated and introduced into a 
glass retort of from 2 to 3 litres capacity, whose outside had been 
previously coated with clay, and carefully distilled. After reject- 
ing the first few Ce. of distillate, the distillation is continued until 
750 Ce. have passed over. 

Dilute sulphuric acid may be prepared by carefully adding 10 Ce. 
concentr. sulphuric acid of spec. gr. 1.840 to 174 Ce. of pure water. 

For volumetric purposes, normal sulphurie acid, containing 48.915 
grammes He S O,zin 1 litre, is prepared by carefully diluting the 
stronger acid so as to accurately saturate an equal volume of 
normal alkali solution. It may be controlled by precipitating with 
barium chloride, and weighing the precipitated barium sulphate. 
100 Ce. norma! sulphuric acid correspond to 11.68 grammes barium 
sulphate. 

Mol. weight of He S Ou=97.824. 


SULPHUROUS ACID, H:2S 0s. 


UseEp to reduce gold, silver and mercury from their salts; to con- 
vert cupric into cuprous salts, chromic acid into chromic oxide, etc. 

PREPARED by saturating pure water with pure sulphur dioxide 
gas, of which about 9.5 per cent will dissolve at ordinary tempera- 
ture, producing a solution of sp. gr. 1.028. 

Pure sulphur dioxide is best obtained by heating pure sulphur or 
copper with pure sulphuric acid. The solution must be carefully 
protected from light and air; if preserved too long, sulphuric and 
pentathionic acids are liable to form. When made by boiling char- 
coal with sulphuric acid it will contain carbonic acid. 

Tests. It must be perfectly clear and colorless, and strongly 
saturated with S Oc. It should not precipitate barium chloride 
previously acidulated with hydrochloric acid. 

On evaporation on platinum foil it must leave no residue. - If not 
known to be made from pure materials, it must be tested for 
arsenic by the methods already described. 


TANNIC ACID,H Cis Ho Oo. 


Digallic Acid or Tannin. 


UsED to precipitate alkaloids, gelatin, albumin, starch; also ferric 
and vanadic salts (blue-black). One drop of its 10% solution added 
to 1 Ce. of centinormal iodine solution forms Griessmayer’s test for 
alkaline hydrates, with which it produces a red color. 

Tests. Pure tannic acid burns completely, leaving no residue. 
With water it must yield a clear, colorless solution, not precipitable 
by alcohol. A solution of 1 part in 5 parts of boiling waver must 


Q* 


24 ACIDS, 


remain clear on addition of a double volume of strong alcohol 
‘absence of gum, dextrine, etc.), also on addition of adouble volume 
of cold water (abs. of resins). 

PREPARATION. Select a pale yellow, light article of commercial 
tannin, with but little odor, tested for purity as above, dissolve 1 
part in 5 parts of cold water, filter and fill up to 10 parts with 10% 
alcohol. If preserved in solution too long it will decompose, form- 
ing gallic acid. 


TARTARIC ACID, Hz Cz: H: Oc. 


UsED occasionally to prevent the precipitation of ferric oxide and 
alumina by caustic alkalies, while other members of the third and 
fourth group are precipitated. Also for acidulation oforganic mix- 
tures in toxicological examinations and to precipitate potassium as 
acid tartrate, for which purpose, however, sodium acid tartrate is 
preferable. To detect iodates in presence of iodides by the yellow 
color surrounding the crystal. 

On account of rapid deterioration of the solution by mould, it is 
kept in a dry state until required, when 1 part is dissolved in 2 parts 
of pure water (or in 5 parts according to U.S. P.) 

Tests. The crystallized acid of commerce is generally found 
sufficiently pure. 

It should leave no residue on ignition. 

It should yield no precipitate with calcium sulphate (absence of 
oxalic acid); nor with silver nitrate (abs. of chlorides); nor with 
barium chloride acidulated with hydrochloric acid (abs. of sul- 
phates). Mol. W.—149.656. 


TITANIC ACID, Hz Ti 04. 


UsEs. Dissolved in concentrated sulphuric acid it gives a red 
brown color to morphine, being a most delicate reagent for it 
(Flueckiger). It also gives with hydrogen dioxide and with barium 
dioxide a very characteristic yellow color, not communicable to 
ether. For this reaction a solution in concentrated sulphuric or 
hydrochloric acid is made, containing 1.5 milligr. titanic acid in 
1 Cc. 


PREPARATION. The minerals rutile, brookite and anatase consist 
of more or less pure titanic acid. They are finely powdered, mixed 
with 10 parts of potassium di-sulphate, and heated in a platinum 
crucible until a clear, glassy mass results. This is powdered and 
extracted with cold water. A drop of sulphuric acid is added to the 
filtered solution, and then hydrogen sulphide passed through for 
some time. The solution is again filtered, and then heated to boil- 
ing for about an hour, while a current of carbonic acid gas is passed 


ACIDS, 25 


through it, the water lost by evaporation being occasionally re- 
placed. This precipitates the titanic acid, which is collected on a 
filter and is sufficiently pure for use. 


TRICHLORACETIC ACID, HC2ClsQ:2. 


UsEp to detect albumen in urine. A crystal thrown into urine 
containing albumen surrounds itself with a white coagulum 
(Raabe). 

Tests. The acid forms transparent rhombohedric crystals, which 
easily deliquesce, melt at 52.3° C., boil at 195° C. Whenheated with 
potassium hydrate solution, chloroform and carbonic acid gas are 
formed. 

PREPARATION. Mix thoroughly a solution of 15 parts of chloral 

hydrate in 15 parts of water, with a solution of 8 parts of potassium 
permanganate in 82 parts of boiling water. The result is the oxida. 
tion of the trichloractic aldehyd (chloral) into the corresponding 
acid, which unites with the potassium, while manganese dioxide 
precipitates. The mixture is filtered, then supersaturated with 
strong (glacial) phosphoric acid and distilled. From the distillate 
the crystals are separated, and, if necessary, purified by redistilla- 
tion. : 
Chloral hydrate may also be converted into trichloracetic acid 
by oxidation with red fuming nitric acid in direct sunlight. 1 part 
of chloral hydrate is added to4 parts red fuming nitric acid, exposed 
to direct sunlight for several days, until no more red fumes are 
given off. The mixture is distilled and the crystals separated as 
before. They are somewhat more difficult to purify from accom- 
panying nitric acid. 

NOTE. Other acids, but rarely employed, or made extemporan- 
eously by adding sulphuric acid to their salts, are 

Formic Acid, H.C H Oz. 


Used in Hampe’s process for separating zinc from other metals. 
It is made by distilling at 100° C. a mixture of equal weights of 
crystallized oxalic acid and glycerin. The commercial article is 
sufficiently pure if entirely volatile. 

Selenic acid, see Sodium selenate. 

Selenous acid, see Ammonium selenite. 

Vanadic acid, see Ammonium metavanadate. 


ALBUMIN. 


Uses. To distinguish meta-phosphoric acid, which forms a pre- 
cipitate with albumin, from ortho- and pyro-phosphorie acids. 
Also to remove tannin from mixtures, etc. 


26 ALCOHOLS. 


PREPARATION. The white of a hen’segg carefully separated from 
the yolk is shaken with about five volumes of pure water and fil- 
tered. Or the commercial dried albumin is dissolved in water. 


ALCOHOLS. 


AMYL ALCOHOL, Cs Hn O H. 
Fusel Oil. 


Usrs. Amylic alcohol is employed as a solvent of alkaloids, also 
to separate urobiline out of urine; also to separate lithium chloride 
from the chlorides of sodium and potassium. 

Tests. Even the purest article of commercial fusel oil contains 
several isomeric alcohols, difficult to separate. The greater part 
consists of iso-amylic alcohol (C Hs)z C H. C He. C He OH, boiling, 
when pure, at 131,69 C., and of spec. grav. 0.811. It should be 
strictly neutral to moist test papers. On evaporation no residue 
must be left. Concentrated sulphuric acid should not give a brown 
color unless heat is applied; while cool, a variety of colors are pro- 
duced, differing according to the proportions of acid and alcohol: 
1 part of acid with 1 part alcohol, cherry red, passing into violet: 
with 5 to 6 parts of alcohol, blue; with 10 or more parts, greenish. 
‘Absence of pyridine and furfurol must be insured by rectification, 
as below described, as their presence would interfere with alkaloid 
reactions. 

PREPARATION. For analytical purposes, amyl alcohol must be 
purified by shaking for some minutes, 100 parts of the alcohol with 
1 part of concentrated sulphuric acid, adding at once 10 parts of 
water; shaking again, and after a short period of rest draining off 
the amylic alcohol floating on the acid mixture. It is then digested 
over some calcium carbonate and hydrate, and then subjected to 
fractional distillation. All th. portion coming over below 181°C. 
is rejected, and only the fraction boiling between 131° and 133°C. is 
preserved. By this cautious fractional distillation, alcohol free from 
pyridine and furfurol may be obtained, suitable for forensic 
analysis. 

ETHYL ALCOHOL, v:H; O H. 


Spirit of Wine. 


Usrp as a general solvent of iodine, potassium or sodium hydrate, 
ammonia, ammonium sulphide, resins, organic acids, alkaloids and 


ALCOHOLS, 27 


various salts; also to separate substances soluble from those insol- 
uble in it; to precipitate from aqueous solution calcium sulphate or 
malate, lead salts, etc.; to reduce oxides, to form with some acids, 
esters recognizable by characteristic odor, such as acetic, salicylic, 
etc. 

It is employed either as absolute alcohol, of spec. gr. 0.7937, boil- 
ing at 78.4°C., or of U. S. P. strength, containing 91% by weight 
(94% by volume) of absolute alcohol, having spec. gr. 0.826 at 
15.6° C. 

For most analytical purposes the ‘‘Cologne spirit” of commerce 
is sufficiently pure. 

Tests. Pure alcohol must be miscible with water in all propor- 
tions without becoming turbid. It must be free from other alco- 
hols (methylic, amylic, ete.), aldehyde and acids, hence, it must be 
entirely neutral to moist test papers; must not be colored on addi- 
tion of potassium hydrate, conc. sulphuric acid, nor silver nitrate 
even after exposure to sunlight; no foreign odor must be perceiv- 
able on evaporation. It must show absence of furfurol by not 
assuming a red color, when 10Cc. are mixed with 1 Ce. of color- 
less aniline oil and 0.5 Ce. hydrochloric acid (Jorissen). 

PREPARATION. Redistil commercial alcohol, rejecting the first 
and last portions, then digest it for 24 hours with 1 gramme potas- 
sium permanganate for each litre and distil again. 

The most concentrated alcohol obtainable by distillation alone 
has spec. gray. 0.825, and contains 89 per cent alcohol by weight. 
To remove the remaining 11 per cent of water, the alcohol may be 
digested with an excess of freshly calcined quicklime for several 
days, replacing the lime daily by a new supply, and finally distil- 
ling it carefully and slowly from a new portion of lime. ‘The first 
four-fifths are quickly transferred to perfectly dry, glass-stoppered 
vials. If carelessly distilled the odor of lime will adhere to the 
alcohol, and moist test papers will show alkaline reaction. 

Absolute alcohol must not change the white color of powdered 
anhydrous copper sulphate to blue. Whenshaken with a few milli- 
grammes of anthraquinone and sodium amalgam the color must be 
green; a red color indicates the presence of water. 


METHYL ALCOHOL, C Hs OH. 
Wood Spirit. 


USED occasionally instead of ethyl alcohol for solutions and sepa- 
rations, also for detecting salicylic acid by the characteristic odor 
of its methyl ester, and for separating boracic acid, which vola- 
tilizes completely by distillation with methyl alcohol. 


28 ALCOHOLS. 


PURIFICATION. Methyl alcohol is seldom found pure in com- 
merce, being usually mixed with a large percentage of acetic acid, 
acetone, tar oils, etc. To free it from these it must first be distilled 
over an excess of quicklime. The distillate is mixed with powdered 
anhydrous calcium chloride, with which it forms erystals of Ca Cle 
+2CHs0O. These are separated from the liquid, dissolved in water 
and distilled, yielding an almost pure methyl alcohol, which is suit- 
able for most purposes. To make it absolutely pure, methyl oxalate 
is prepared from it by distilling it with an equal weight of conc. 
sulphuric acid and twice its weight of potassium acid oxalate. 
Methy) oxalate, on cooling, forms colorless crystals, and these on 
redistilling with water yield pure methyl alcohol and oxalic acid. 

Tests. Absolute methyl alcohol boils at 65.5° C., and has specific 
grav. 0.798 at 20° C. 

In5 Cc methyl alcohol dissolve 0.1 gramme iodine and add solu- 
tion of potassium hydrate till the brown color disappears. If ace- 
tone was present, a yellow precipitate of iodoform will fall. 

The color of moistened test papers should not be changed. 


GLYCERIN, CsHs(0OH)s. 


Propenyl Alcohol. 


UsED as a solvent and to detect boracic acid by flame test, etc. 

Tests. Pure glycerin is a colorless, inodorous, thick liquid of 
sweet taste and neutral reaction, miscible with water in all propor- 
tions. 

The best quality of the commercial article is sufficiently pure for 
use. 


ALLOXANTIN, Cs Hs Ns 07 + 3 He O. 


Usss. To distinguish cotton from woolen fabrics. If a piece of 
mixed cloth is moistened with a solution of 1 part of alloxantin in 10 
parts of warm water, dried, and then exposed to ammonia vapor, the 
woolen is colored crimson, the cotton remains white (Overbeck). 

PREPARATION. One part of nitric acid, spec. gr. 1.42, is diluted 
with eight parts of water, heated to 60° C., and saturated with uric 
acid. It is then heated to boiling and a concentrated solution of 
stannous chloride, mixed with an equal volume of hydrochloric 
acid is added as long as a precipitate falls. An excess of stan- 
nous chloride is indicated by the production of a yellow color- 
The precipitate is collected on a filter, washed with very cold water, 
in which it does not readily dissolve, and then dried. 


ALUMINIUM, 29 


ALUMINIUM. 


Usrs. The pure metal in thestate of foil, ribbon or wire is used 
to generate pure hydrogen from a solution of potassium or sodium 
hydrate. Hence, it is employed in Zatehouse’s modification of 
Flettmann’s test tor arsenic. Also used to reduce nitric acid to 
ammonia. 


Tests. In a solution of potassium hydrate it must be soluble 
without residue. The gas evolved during the solution must not 
blacken paper moistened with silver nitrate or lead acetate solu- 
tion. 


ALUMINIUM SULPHATE, Ale (S Oz)s + 18 He O. 


Uses. In microchemical detection of potassium salts, by forming 
with them alum crystals, recognized under the microscope by their 
octohedral form. Also to distinguish eosine from other dyes on 
textile fabrics. A hot solution of 1 part aluminium sulphate in 4 
parts water removes the color of cochineal and other red lake dyes; 
coal-tar colors, such as corallin, fuchsin, saffranin, ete., are dis- 
solved, while eosin remains unaffected (Dyer’s Gazette). Also to 
precipitate albumen. 

Tests. The commercial salt, obtained by solution of clay or 
bauxite in sulphuric acid, or as a bye-product of the soda manufac- 
ture from kryolite is sufficiently pure, when free from iron. 


PREPARATION. On the small scale it is obtained in precipating 
alum solution by ammonia, separating the aluminium hydrate by 
filtration, washing it thoroughly, and dissolving in pure sulphuric 
acid to neutralization. 


NOTE. Alum, either the potassium aluminium sulphate or the 
corresponding ammonium salt, is sometimes, but rarely, used for 
similar purposes. Tbe commercial salt, purified by repeated crys- 
tallization, or the U.S. P. salt may be used. 


AMALGAMS. 


These are alloys of various metals with mercury. The principal 
ones employed are copper amalgam for use with hydrobromic acid, 
to remove sulphur from sulphides, and sodiwm amalgam as a gene- 
ral reducent, by the introduction of nascent hydrogen, especially 
in organic compounds. They are described under the headings of 
the respective metals. 


80 AMMONIUM AND AMMONIUM COMPOUNDS. 


AMMONIA AND AMMONIUM COMPOUNDS. 


AMMONIA, N Hs; AMMONIUM HYDRATE, N Hs 0H. 
Aqua Ammonia. 


Uses. The watery solution of ammoniacal gas, N Hs, usually 
called ammonium hydrate, is a reagent of great importance and 
generai utility. It serves to neutralize acids, to precipitate the 
bases of many salts and to recognize some of them by characteristic 
colors; also to separate the insoluble hydrates of iron, aluminum: 
etc., from those of zinc, nickel, cobalt, copper, ete., which 
are soluble in ammonia; also to separate the soluble chloride, 
from the insoluble iodide of silver, etc., etc.; also as volumetric so- 
lution in acidimetry. 

The U.S. P. prescribes two preparations of different strength: 
Ammonia water of spec. grav. 0.9598, containing 10% of gas in 
solution, and suitable for most purposes in analysis, and stronger 
ammonia water of spec. grav. 0.9026, containing 28% of gas in solu- 
tion. Of the first 17 grammes saturate 100 Ce. normal acid solution, 
of the latter 6.07 grammes only are required. M. W.=17.021. 

Tests. The colorless solution must leave no residue on evapora- 
tion. It must be free from carbonate, hence, solution of calcium or of 
barium hydrate mustnotrenderit turbid. In ammonia supersatur- 
ated with nitric acid neither silver nitrate nor barium chloride must 
produce a precipitate (absence of chloride or sulphate). Hydrogen 
sulphide must produce neither coloration nor precipitate. Neither 
odor nor color must appear on neutralization with dilute sulphuric 
or hydrochloric acids, red color showing presence of pyrrol, brown 
of tar oils, ete. 

PREPARATION. It will seldom be necessary to prepare ammonia 
on the small scale, as a very pure article is readily found in the 
market. When needed, 5 parts of freshly burnt lime are moistened 
sufficiently to slack and fall into powder. With this, 4 parts of 
granulated ammonium chloride are thoroughly mixed, and suffi- 
cient water added to form loose lumps. These are introduced into 
a flask, resting on a sand bath, and connected by glass-tubing with- 
out rubber joints, with one or, still better, two small wash bottles, 
and lastly, with a well-cooled receiver, containing ten parts of pure 
water. The wash bottles are partially filled with a small quantity 
of water, kept at a temperature of 90° to 98° C., so as to prevent the 
passage of pyrrol, aniline and similar volatile products into the 
receiver. The solution in the receiver is, at the close of the distil- 
lation, diluted to the required strength and kept in small vials, 
whose glass stoppers are coated with paraffin to prevent adhesion 
to neck. 


AMMONIA AND AMMONIUM COMPOUNDS: 31 


Sometimes alcohol is saturated with the gas and used under the 
name of Liquor Dzondw. In connection with lead acetate, it serves 
to precipitate lactic acid. The U.S. P. spiritusammonie, contain- 
ing 10% of gas, is suitable for this purpose. 


Volumetric Solutions of Ammonia. 


The volatility of ammonia makes it difficult to preserve, for any 
length of time, a uniform amount of gas in concentrated solutions, 
and hence, though these are occasionally employed for special 
purposes, the half-normal solution is most frequently used on 
account of less liability to alter its titre, either from loss of gas or 
from absorption of C O2 from the air. 

Half-Normal Solution of Ammonia, containing 8.5 grammes 
NHs per litre. Astronger solution of ammonia is diluted until 
100 Ce. accurately saturate 50 Cc. of Normal acid solution (either 
sulphuric, hydrochloric or oxalic), rosolic acid or cochineal solu- 
tion being used asindicator. 

Normal Solution, containing 17 gr. N Hs, and five-times normal, 
containing 85 gr. N Hsin 1 litre, are occasionally used in water 
analysis, and prepared in same manner as the half-normal. 


AMMONIUM BENZOATE, N Hz C7 Hs O02. 


UsED in separating copper from cadmium; copper benzoate being 
soluble, cadmium insoluble ina 10 % solution of ammonium ben- 
zoate (Gucct). 

Tests. The U.S. P. salt is sufficiently pure. It forms colorless 
crystals, readily soluble in water and in aleohol. On heating they 
fuse, then give off vapors of benzoic acid and ammonia, and leave 
no residue. Its dilute solution should not, after acidulation with 
nitric acid, give a precipitate with barium chloride or silver nitrate. 

PREPARATION. Dissolve8.5 grammes of pure benzoic acid in suf- 
ficient ammonia water to neutralize accurately, and dilute with 
distilled water to 100Cc., or make a 10% solution of the crystals. 


AMMONIUM CARBONATE, (N H,)2 C Os, 


Usrs. This reagent precipitates many metallic salts from their 
solutions as carbonates. It is especially employed in systematic 
analysis as the general precipitant of barium, strontium and cal- 
cium, which it serves to separate from magnesium and the alkalies. 
.Also used to separate arsenic sulphide by solution from insoluble 
antimony sulphide, etc. 

Tests. After removing the outer crust of the commercial article 
(purified by resublimation), so as to reject the outer layer of ammo- 


nium dicarbonate and accidental impurities adhering to it, the crys- 


32 AMMONIA AND AMMONIDPM COMPOUNDS 


talline mass must be completely volatilized by heat. It must be 
free from empyreumatic odor; after addition of a slight excess of 
nitric acid, neither hydrogen sulphide, barium chloride, nor silver 
nitrate, must produce a precipitate. A solution in water must not 
blacken ferric chloride. 


PREPARATION. Onthe large scale, ammonium carbonate is made 
by subliming 1 part of crude ammonium chloride with two parts of 
chalk, or four parts of ammonium sulphate with four parts of chalk 
and one part of charcoal. This product must be resublimed, and, 
if not found in commerce of sufficient purity, must again be puri- 
fied by careful resublimation. It consists principally of ammonium 
dicarbonate and ammonium carbamate : NH,HC0O3s+N H4 CO, 
N He. By solution in water, or in contact with moist air, the car- 
bamate is converted into carbonate, and the dry commercial pro- 
duct, in undergoing this change, surrounds itself with a white 
pulverulent crust of dicarbonate. Theinner crystalline part, shown 
to be free from chloride, sulphate, sulphide and hyposulphite, by the 
tests above described, is used for the solution by adding to 1 part of 
it amixture of 1 part of 10% ammonia water with 4 parts of pure 
water. The solution contains neutral carbonate in about double 
normal strength (192 gr. in 1 litre). 

A mixture of 391 Ce. of 10% ammonia water with 235 Ce. of this 
solution of carbonate is diluted with pure water to make 1 litre, and 
ismuch employed under the name of Schaffgol’s solution in techni- 
cal laboratories for the precipitation of magnesia in the analysis of 
alkalies. 


AMMONIUM CHLORIDE, N Hs Cl. 


Sal Ammoniac. 


Usres. The solution of ammonium chloride serves to retain in 
solution magnesium and manganous carbonates and hydrates, etc., 
while barium, strontium, calcium, aluminium, ferric salts, etc., are 
precipitated by ammonium carbonate and hydrate. From alkaline 
solutions it precipitates aluminium hydrate, etc.; from neutral and 
acid solutions, platinum and iridium as double chlorides. N H4 Cl 
= 53.321. 


Txests. Not a trace of residue must be left when ammonium 
chloride is heated on platinum foil. At ordinary temperatures it 
must form a perfectly clear solution with 4 parts of pure water. 
In dilution of 1 to 20 no precipitate must be formed with hydrogen 
sulphide, dilute sulphuric acid or barium chloride ; nor must ferric 
chloride, potassium ferrocyanide or tannic acid produce either col-. 
oration or precipitate after acidulation with hydrochloric acid. On 


AMMONIA AND AMMONIUM COMPOUNDS. 8% 


evaporation with nitric acid no brown tint nor empyreumatic odor 
should appear. 


PREPARATION, When pure ammonium chloride cannot be ob- 
tained, the best commercial article may be purified either by care- 
ful resublimation, or by making a saturated solution in boiling 
water, adding to this a little chlorine water, so as to convert fer- 
rous salts into ferric, and then adding a slight excess of ammonia 
water, so as to precipitate ferric hydrate. The liquid is heated to 
expel all the excess of ammonia, the precipitate is separated by fil- 
tration and the filtrate set aside to crystallize, being occasionally 
stirred to prevent the formation of large crystals. Thecrystals are 
drained on a funnel; if not yet entirely pure they are recrystal- 
lized; 1 part of the dry salt is dissolved, for ordinary use, in 8 parts 
of pure water. 

A volumetric solution of jive-times-normal ammonium chloride, 
made by dissolving 266.96 grammes of the pure dry salt in water 
and diluting so as to fill 1 litre, is used in water analysis for the 
separation of calcium from magnesium. 


AMMONIUM CITRATE, '(N Hg)s Co Hs O7. 


UsEs. In the analysis of phosphates and phosphatic fertilizers, 
solutions of ammonium citrate are used in two degrees of concen- 
tration. 

There are 8 varieties of calcium phosphate, the primary, Ca H4 
(P O4)2, also called the acid or monobasic, soluble in water; then 
the secondary, Ca H P Ou, also called the dibasic or neutral (the so- 
called ‘“‘reduced” phosphate, which is insoluble in water, but sol- 
uble in solution of ammonium citrate ; the third is the tertiary, Cag 
(P O42, also called tribasic, which is insoluble in either water 
or ammonium citrate. Mol. W. = 188.564. 


PREPARATION. For the concentrated solution, 100 grammes of 
pure citric acid are dissolved in a mixture of 100 Cc. pure water 

and 120 Cc. ammonia water of 10%. The solution is then accurately 
neutralized by addition of ammonia water, poured into a 1 litre 
flask and filled up to the mark with water. 

The dilute solution for washing is made by diluting 1 part of the 
concentrated solution with 2 parts of water. 

Ammonium-magnesium citrate solution is sometimes used for the 
precipitation of phosphoric acid, and is prepared as follows: 27 
grammes pure magnesium carbonate are added gradually to a hot 
solution of 270 gr. citric acid in 350 Cc. water; after solution, 400 
Cc. ammonia water of 10% are added, and the mixture filled up 
with water to 1 litre. 


34 AMMONIA AND AMMONIUM COMPOUNDS. 


AMMONIUM FLUO-BORIDE OR BORO-FLUORIDE, N Hi F. B Fs. 


Uses. Ammonium or sodium boro-fluoride, which are quite sol- 
uble in water, form, on adding them to potassium salts, precipitates 
of potassium boro-fluoride, requiring 223 parts of cold water for 
their solution; soluble in 16 parts of boiling water (Stolba). 

Tests. No precipitate should be produced by hydrogen sulphide 
or ammonium sulphide. As the reagent is only used for qualitative 
work, the presence of some silico-fluoride and borate is not objec- 
tionable. 

PREPARATION. The first step is the preparation of hydro-fluo- 
boric acid, by heating 1 part of powdered boric anhydride, obtained 
by fusing boracic acid (or instead thereof 2 parts of powdered borax: 
glass) with 2 parts of finely powdered fluorspar and twelve parts 
of concentrated sulphuric acid. 

Boron trifluoride, B Fs, is formed, a colorless gas, fuming in air, 
which is conducted by a glass tube into 10 parts of distilled water, 
in which it readily dissolves, forming a dense solution, intensely 
acid, containing boric and hydro-fluo-boric acid. ; 

This is carefully saturated with strong ammonia water (or, if the 
sodium salt is required, with the sodium carbonate). 


AMMONIUM HYDROGEN FLUORIDE, NH: F. HF. 


Uses. For the decomposition of silicates, titanates, tin stone, 
chromic iron ore, etc., instead of hydrofluoric acid or potassium 
hydrogen fluoride (Gzbbs). 

Tests. Neither hydrogen sulphide, ammonium sulphide, am- 
monia, ammonium carbonate, nor sodium phosphate with ammonia 
should produce a precipitate. No residue must be left on evapora- 
tion. 

PREPARATION. In a platinum vessel pure hydrofluoric acid is 
supersaturated with ammonia and carefully evaporated. Hydro- 
fluo-silicic acid can also be used, the precipitate being separated by 
passing through a filter previously washed out with hydrofluoric 
acid. Commercial salt may be purified by precipitating and filter- 
ing just like hydro-fluo-silicic acid. Itis best to prepare the reagent 
only in sufficient quantity for present use, as it must be preserved in 
guttapercha vessels, and, if kept in glass, attacks it, becomes con- 
taminated and must be purified. 


AMMONIUM HYPOSULPHITE, (N H4)z Se Os. 
Ammonium Thio-Sulphate. 


Uses. Ammonium hyposulphite has been proposed (as well as 
other hyposulphites) to serve as a general reagent, instead of hydro- 


AMMONIA AND AMMONIUM COMPOUNDS. 85 


gen sulphide, for separating metals into analytical groups; also as 
aspecial reagent for separation of cadmium from copper (Orlowsk7). 
From solutions acidulated with H Cl it precipitates the same 
metals as HeS, excepting lead, tin, antimony and cadmium. 

Tests. Ammonium hyposulphite forms colorless, deliquescent 
crystals, which must volatilize at high heat without residue. Sil- 
ver nitrate produces in its solution a white precipitate, turning 
black after awhile, or immediately on application of heat. Hydro- 
chloric acid, added to solution, leaves it clear at first, but soon, es- 
pecially on heating, precipitates sulphur, while sulphur dioxide 
escapes. 

PREPARATION. In milk of lime, made by mixing 100 parts of 
freshly slaked lime in fine powder with 500 parts of water, 90 parts 
of sulphur are boiled for some time, replacing the water as it 
evaporates. The solution after cooling is decanted, and saturated 
with sulphur dioxide gas, until the yellow color disappears and 
sulphur is no longer precipitated. It is then filtered and a concen- 
trated solution of ammonium carbonate is added as long as calcium 
carbonate precipitates. The liquid is filtered, concentrated by 
evaporation on water bath, and set aside to crystallize. The crys- 
tals are purified by recrystallization, and 1 part is dissolved for 
use in 5 parts of water. In nearly all cases, sodium hyposulphite 
may be used instead of the ammonium salt. 


AMMONIUM META-VANADATE, N Hz V Os. 


Uses. When dissolved in sulphuric acid, ammonium meta-vana- 
date serves to detect a number of alkaloids by very characteristic 
color reactions—colchicin, blue-green; gelsemine, purple; hydras- 
tine, carmine red; narcotine, vermilion; piperine, blood red, then 
black; strychnine, violet-blue, changing to red; etc., etc. (Man- 
delin.) 

Tests. Absence of nitric acid must be shown by any of the vari- 
ous tests. Absence of chromium is shown by dissolving in dilute 
hydrochloric acid and adding hydrogen dioxide, freshly prepared 
from barium dioxide and dilute hydrochloric acid. Pure vana- 
dates produce a red color, not communicated to ether, which re- 
mains colorless when shaken with it, while the presence of chro- 
mates is revealed by a blue color, communicated to ether. Absence 
of lead is shown by He S in acid solution, that of iron by potassium 
ferrocyanide or other tests. 

PREPARATION. Lead vanadate or other rich vanadium ores are 
finely powdered, mixed with saltpetre and fused. The melied mass 
of impure potassium vanadate is dissolved in water, filtered, neu- 
tralized by nitrie acid and precipitated by barium chloride. The 


BE AMMONIA AND AMMONIUM COMPOUNDS, 


impure barium vandate is washed and then decomposed with dilute 
sulphuric acid. The barium (and lead) sulphate is removed by fil- 
tration, the filtrate is neutralized with ammonia water, and then 
concentrated by evaporation. A solid piece of ammonium chloride 
is placed into the solution, which gradually dissolves, and thereby 
separates from it granules of white ammonium meta-vanadate, 
The salt is washed with concentrated solution of ammonium chlo- 
ride, in which it is insoluble; it is then dried and, if necessary, 
purified by recrystallization. For use 1 part is dissolved i in 200 
parts of pure sulphuric acid of spec. gr. 1.77, and preserved in glass- 
stoppered vials. 


Ammonium Molybdate, see molybdre acid, ec. 
AMMONIUM NITRATE, N Hz: N Os. 


UsEs. In dry substance, to oxidize metals, carbon, etc., to facilitate 
the combustion of filters ; also in solution in the molybdate proc. ss 
for determining phosphoric acid. Mol. W. = 79.922. 

Tests. No residue must be left on heating upon platinum foil. 
No precipitate in watery solution, acidulated with nitric acid, by 
silver nitrate, nor by barium chloride. 

PREPARATION. Pure ammonium carbonate is saturated with 
_ pure nitric acid, and heated to expel carbon dioxide; then some 
ammonia water is added to alkaline reaction, and the clear 
solution set aside to crystallize. The crystals are dried, fused in a 
platinum dish, and preserved in glass-stoppered bottles. 


AMMONIUM OXALATE (NHs4)2 C2 Os + He O 


Usses. To precipitate the salts of metals, especially those of cal- 
cium ; to separate calcium, barium, zinc and lead, which form in- 
soluble oxalates from vanadic acid, which remains in solution 
(Halberstadt); to separate calcium from strontium by a solution 
containing 30 gr. ammonium oxalate and 200 gr. ammonium sul- 
phate in 1 litre of water (Stdersky). Mol. W. = 141.78. 

Tests. The salt on ignition upon platinum foil must volatilize 
completely. No precipitate must be formed in its solution by hy- 
drogen sulphide or ammonium sulphide. The precipitates by bar- 
ium erlones and by silyet* nitrate must completely redissolve in 
nitric. acid. 

‘PREPARATION. The solution may be made by dissolving 1 ‘part 
of pure oxalic acid in 21 parts of water, adding 4 parts of ammonia 
water of 10%, and heating long enough to expel the excess of am- 
monia. If much water is lost by evaporation it must be restored, 
so as to make 25 parts of solution, as ammonium oxalate is not sol- 
uble in a less quantity of water. 


AMMONIA AND AMMONIUM COMPOUNDS, 37 


The crystals are prepared by supersaturating a hot saturated so- 
lution of pure oxalic acid in water with strong ammonia water, 
boiling to expel excess of ammonia and setting aside to crystallize. 
1 part of the crystals is dissolved in 24 parts of pure water. 

Volumetric solution of ammonium oxalate for titration of alumin- 
ium salts, etc., contains for deci-normal strength 14.2 gr. erystal- 
lized ammonium oxalate in 1 litre. Calcium chloride serves as 
indicator. 


AMMONIUM PHOSPHATE, (NHa)s P 04+ 3 He O. 


Uses. For precipitation of magnesia, when the introduction of 
sodium phosphate is to be avoided on account of subsequent search 
after alkalies. 


Tests. Absence of metals is shown by precipitating from the 
aqueous solution all the phosphoric acid by lead acetate, removing 
any excess of lead by hydrogen sulphide and evaporating the fil- 
tered solution. No residue must be left on heating upon platinum 
foil. Absence of arsenic is to be proved by Fleitmann’s test (see 
nitric acid, page 14) ; absence of sulphates by barium chloride after 
acidulation with nitric acid. 


PREPARATION. Fifteen Ce. of pure phosphoric acid, of spec. 
gray. 1.347 (U. S. P. strength), are slightly supersaturated with 
ammonia water, and then diluted with distilled water to 100 Ce. 
The dry salt is obtained by saturating pure phosphoric acid with 
strong ammonia water, evaporating until it begins to solidify, 
mixing again with a slight excess of strong ammonia water and 
setting aside to crystallize. The crystals must be preserved in well- 
closed bottles, as they lose ammonia and gradually form the sec- 
ondary salt, (N H4)2H P O4.. One part is dissolved for use in 10 
parts of pure water. 


AMMONIUM SELENITE, (N H4)z Se Os. 


Uses. Selenous, as well as selenic acid, or rather the solutions of 
their alkali salts in sulphuric acid, have recently been used in the 
analysis of alkaloids, etc. Elaterin, colocynthin and hydrastine give 
peculiar color reactions (Johannson); codeine produces, even in 
minimal quantities, a green color (Lafon), etc. 


PREPARATION. Powdered selenium is dissolved in concentrated 
nitric acid, which oxidizes it to selenous acid, H2Se Os. The solu- 
tion is evaporated to dryness, and the acid may be thus preserved 
or dissolved in water, saturated with ammonia and crystallized. 
Both the acid and the ammonium salt must be carefully protected 
from light and contact with seca eens See also sodiwm selenate. 


38 AMMONIA AND AMMONIUM COMPOUNDS. 


AMMONIUM SUCCINATE, (N Ha)e2 C4 Ha O14. 


Usss. In quantitative analysis, to separate ferric and aluminium 
salts as insoluble succinates from zinc, manganous, nickelous and 
cobaltous salts, whose succinates are soluble, 

Tests. The salt erystallizes in long, colorless, triclinic prisms, 
which, by long keeping, lose ammonia, forming the acid salt. It 
must leave no residue on heating upon platinum foil. A concen- 
trated solution, when mixed with concentrated potassium acetate 
and some acetic acid, should not yield a precipitate of cream of 
tartar (absence of tartaric acid). After acidulation with nitric 
acid, neither silver nitrate nor barium chloride should produce a 
precipitate. When heated with indigo solution and sulphuric acid 
it should not discharge the blue color. 


PREPARATION. The crude acid, of which about 4 per cent are ob- 
tained by the dry distillation of amber, is freed from oil by 
solution in hot water, filtration, concentration and crystallization. 
After recrystallization, the ‘acid is dissolved in dilute nitric acid, 
heated and repeatedly recrystallized untila white product free from 
empyreuma is obtained. Care must be taken to wash the crystals 
so as to remove nitric acid. It is then supersaturated with am- 
monia water, crystallized (and recrystallized, if necessary) and the 
dry salt preserved for use in well-closed bottles to prevent loss of 
ammonia. For use, 1 part is dissolved in 10 parts of water, ren- 
dered slightly alkaline by ammonia. 


AMMONIUM SULPHATE, (N H:)2S Os. 


Uses. To introduce sulphuric acid without disturbing the neu- 
trality, as in precipitating barium, etc. To separate, in conjunc- 
tion with ammonium oxalate, calcium from strontium. To precipi- 
tate urates and albumoses in urine. 

Tests. Ammonium sulphate forms colorless, rhombic crystals, 
soluble in two parts of cold water. It should be completely vola- 
tilized by heat, decomposing into ammonia, free nitrogen, water 
and ammonium sulphite, which sublimes. As the commercial salt 
is difficult to purify, itis best to make it from pure materials. 

PREPARATION. Pure dilute sulphuric acid is fully saturated by 
gradual addition of ammonia water. The neutral solution is evap- 
orated and crystallized. 


AMMONIUM SULPH-HYDRATE, N Hi: HS; AMMONIUM SULPHIDE 
(N Haz S; AND AMMONIUM POLYSULPHIDE, (N Hs4)2 Sx. 


Uses. Ammonium sulphide and sulph-hydrate are generally 
employed either indiscriminately or in a mixture containing vari- 


AMMONIA AND AMMONIUM COMPOUNDS, 39 


able quantities of both. They serve to precipitate the metals of the 
third (or aluminum) group as hydrates, and those of the fourth (or 
iron) group as sulphides. 


Mixed with the yellow polysulphide they are used to separate the 
sulphides of the sixth (or arsenic) group, which dissolve from those 
of the fifth (or copper) group, which are insoluble in ammonium 
sulphide ; also in organic analysis, e. g., to recognize chloral hy- 
drate by a characteristic precipitate. Occasionally an alcoholic 
solution is substituted for the aqueous one. 


Tests. Ammonium sulphide and sulph-hydrate must not con- 
tain ammonium carbonate or free ammonia; hence, solutions of 
calcium or magnesium salts must not be rendered turbid by them, 
even when heated. They must be perfectly volatilized on heating. 
Hydrochloric acid should not produce any precipitate in the color- 
less sulphide or sulph-hydrate, and only a white precipitate of pure 
sulphur in the yellow polysulphide. Purity is best insured by using 
for their preparation pure materials, careful washing of the gas and 

full saturation. 


PREFARATION. Hydrogen sulphide, made as directed in the article 
treatiny of that reagent,(HeS, page 10), is passed through a wash-bottle 
and into a bottle containing pure 10% ammonia water until it ceases 
to be absorbed. The liquid consists now of a solution of ammonium 
sulph-hydrate. This may be preserved and used as it is, but gene- 
rally it is converted, at least partially, into sulphide by the addition 
of more ammonia water. If this be added in too large a quantity, 
or if the saturation at first was incomplete, free ammonia will be 
present in the mixture, which would lead to errors in analysis. 
Hence, it is best to use only enough ammonia water to partially 
convert the sulph-hydrate. Theory requires exactly the same 
amount of ammonia to be added as that which was first taken for 
saturating with the gas. Usually, 3 volumes of the sulph-hydrate 
are mixed with 2 volumes of ammonia water of the same strength 
as that used at first. 


The colorless product should be preserved in small bottles, well 
protected from air and light, for exposure decomposes it and ren- 
ders it yellow. 


At first, only a polysulphide is formed, but soon more oxygen is 
absorbed and polythionates form, which render its use objection- 
able. 


To make the yellow polysulphide, pure sulphur should be di- 
gested with the above solution of sulphide, and tbe clear liquid 
decanted from undissolved sulphur and well preserved. 


3* 


40 AMMONIA AND AMMONIUM COMPOUNDS. 


AMMONIUM SULPHOCYANATE, NH: CNS. 
(Sulphocyanide, Thiocyanate or Rhodanate.) 


Usss. The soluble sulphocyanates, especially the potassium and 
ammonium salt, are used to detect ferric salts, and distinguish 
them by their intense red color from the colorless ferrous. Also to 
precipitate from cupric salts in presence of a reducent, such as SOx, 
white cuprous rhodanate. Alsoin the volumetric silver assay by 
Volhard’s process. 

Presence of calcium, strontium, barium, magnesium and some 
other chlorides interferes with the ferric reaction, and in small 
quanties prevents it entirely. Mol. W. = 76.0. 

Tests. The watery solution must remain clear and colorless on 
addition of hydrochloric acid. With silver nitrate it must form a 
pure white precipitate completely soluble in ammonia water. 

PREPARATION. To 4 parts of pure carbon disulphide add 15 parts 
each of strong alcohol and concentrated ammonia water. Mix 
well, and leave them to digest for several days. Two-thirds of the 
mixture are then removed by distillation; the remaining third is 
filtered, concentrated and at last set aside to crystallize, under a 
bell glass, over sulphuric acid. Colorless, very deliquescent 
crystals will form, which must be purified by recrystallization. In 
all these operations, too high a temperature must be avoided, 
otherwise the salt will decompose, forming thio-urea, ete. 

Another mode of preparation consists in digesting a mixture of 
hydrocyanic acid and yellow ammonium polysulphide, the 
latter being in some excess. After some days standing, the excess 
of ammonium sulphide is removed by heat, and the crystals are ob- 
tained as in the other method. They must be preserved in well- 
closed bottles, as they rapidly attract moisture from the air and 
dissolve in four-fifths of their weight of water. 

Decinormal Solution is made by dissolving eight grammes of the 
salt in one litre of water, and diluting, so as to correspond accu- 
rately with decinormal solution of silver nitrate. A 10% solution of 
ferric alum is used as indicator. 


ANILINE COMPOUNDS. 


ANILINE, Ce Hs N He. 
Amido-Benzol 


Usss. Aniline, dissolved in alcohol, is used to detect chloroform, 
chloral, etc., by the production of the characteristic isonitril odor, 


ANILINE COMPOUNDS. 41 


when heated together with them and a solution of an alkaline hy- 
drate (Hoffman). A solution of 0.5 Ce. of pure colorless aniline in 
15 Ce. of alcohol and 15 Ce. of concentrated ether, is used to detect 
minute quantities of fluorine in silicates by passing through it the 
vapor evolved when the silicate is heated with sulphuric acid. 
Aniline silicofluoride is formed, and afterward converted into 
sodium silicofluoride by addition of sodium hydrate dissolved in 
absolute alcohol (A7op). 

A mixture of 1Cc. of colorless aniline oil with 0.5 Ce. of hydro- 
chloric acid forms Jorissen’s test for furfurol in fermented and dis- 
tilled liquids. This quantity is added to ten Cc. of the alcohol, 
whiskey, etc., to be tested, and shows the presence of furfurol, 
Cs H4 O2 (pyromucic aldehyde), by a rosered color. 

In saturated aqueous solution, aniline serves to dissolve gen- 
tiana violet, fuchsin, etc., for the staining of micro-organisms. 
Also used in the preparation of aniline sulphate, hydrochlorate and 
other salts and derivatives. 

Filter paper, saturated with aniline oil, neutralized with hydro- 
chloric acid, indicates ozone in gas mixtures by assuming a brown 
color (Wagner). The browning of colorless aniline oil under in- 
fluence of air and light is attributed by Schoenbein to ozone, but is 
not as sensitive a test as the hydrochlorate. 

It is also used in gas analysis in the place of glacial acetic acid, 
as an absorbent of cyanogen in mixtures of gases (Jacquemin). 

Also for the volumetric determination of nitrous acid, based upon 
the formation of di-azo-benzol (Green and Rideal). Mol. W = 92.865. 


Tests. For most purposes the commercial aniline oil is suffi- 
ciently pure, when recently distilled and colorless; for making the 
sulphate for the nitric acid test it is even preferable on account of 
containing para-toluidine. Pure aniline is a colorless liquid of spec 
gr. 1.0276 at 12°C. It dissolves in 31 parts of water at 12.5° C., is 
miscible with alcohol in all proportions. Its reaction is feebly 
alkaline, discernible by dahlia paper, but not by litmus. With 
sodium hypochlorite in dilute solution it gives a purple violet 
color. It must be proven free from arsenic by Fleitman’s test. 


PREPARATION. On the large scale, aniline is made by reducing 
nitro-benzol with nascent hydrogen from iron chips and hydro- 
chloric acid, then adding lime and distilling. When absolutely 
pure materials are used this furnishes pure aniline. But when the 
nitro-benzol has been made from impure benzol, or when arsenic 
trioxide has been used in the manufacture, the crude oil must be 
purified. The removai of ortho-toluidine is accomplished by satu- 
rating the aniline oil with hydrochloric acid, then adding sodium 
phosphate to decompose the salt. The mixture is kept warm and 


42 ANILINE COMPOUNDS. 


separates into two layers; the lighter. containing the oily ortho- 
toluidine, is removed, and the heavier residue is set aside to cool, 
when crystals of aniline, and para-toluidine phosphate are formed. 
These are purified by recrystallization, then decomposed by sodium 
hydrate and distilling (L. Levy). The distillate is reduced to the 
temperature of 10° C., when most of the paratoluidine crystallizes, 
its melting point being 45° C., while aniline remains liquid down to 
8°C. The liquid aniline is separated by filtration, and may be fur- 
ther purified by fractional distillation, preserving the fraction, 
coming over at 182.5° to 184° C. 

Perfectly pure aniline may be made, on a smaller scale, by using 
pure acetanilide (antifebrine), which is easily purified by recrystal- 
lization from benzol and by distillation at 295° C. The pure acetan- 
ilide is decomposed by sodium hydrate and the aniline distilled off 
and rectified by redistillation. 

Decinormal Solution for the analysis of nitrites is made by mix- 
ing 9.38 grammes of pure aniline oil with 100 Ce. of normal sulphuric 
acid and 100 Ce. normal hydrochloric acid, and filling up to 1 litre 
with distilled water. Starch solution, with potassium iodide, isused 
as indicator. A normal solution is more recently used containing 
93 gr. aniline and 450 Ce. hydrochloric acid in 1 litre. 


ANILINE SULPHATE, (Ce Hs N He)2 He $04, 


Ussrs. Aniline sulphate, containing para-toluidine sulphate, is 
used in solution in strong sulphuric acid to discover small traces of 
nitrates (in drinking water) by the production of an intense red 
color. Pure aniline sulphate hardly shows the reaction, but when 
mixed with paratoluidine the reaction is more distinct than with 
either reagent alone. Nitrites, in concentrated solution, produce 
with it a yellowish brown; in dilute solutions, a faint yellow color, 
due to the formation of diazobenzol. With chlorates, bromates, 
iodates and hypochlorites violet to blue colors are produced, with 
chromates, permanganates and vanadates, orange changing to 
violet. 

Aniline sulphate forms a valuable reagent for recognition of wood 
pulp in paper, as it colors the lignin a golden yellow, while pure 
cellulose remains unaffected. 

A decinormal solution containing 14.2 gr. aniline sulphate and 
3.65 gr. hydrochloric acid in 1 litre has been proposed for the titra- 
tion of nitrites (Grecn & Rideal), but is little used on account of 
the difficulty of avoiding sources of error. 

Tests. Aniline sulphate is readily soluble in water and acids, 
less in strong alcohol, insoluble in ether. Its solution colors pine 


ANILINE COMPOUNDS. 48 


wood intensely yellow, produces with hypochlorites a violet color, 
with solution of potassium dichromate and sulphuric acid, first an 
orange then a blue. The commercial salt is sufficiently pure. 

PREPARATION. For most purposes a solution of 1 part aniline oil 
in 99 parts of concentrated sulphuric acid answers best. 


p AMIDO.DIMETHYL-ANILINE, Ce Hs. N He N (C Hs)e. 
Dimethyl-para-phenylen-diamine. 


Usss. In conjunction with ferric chloride and hydrochloric acid, 
to detect, by the production of methylene blwe, even such minute 
traces of hydrogen sulphide as would escape detection by lead salts 
or other reagents (Caro and Fischer). To about 50 volumes of the 
aqueous solution, suspected of containing Hz S, one volume of con- 
centrated hydrochloric acid is added, and then a few vranules of 
para-amido-dimethyl-aniline, or its sulphate or hydrochlorate. 
After solution, a drop or two of dilute solution of ferric chloride is 
added. If hydrogen sulphide was present the liquid, after a little 
time, assumes a deep blue color. The addition of hydrochloric 
acid is necessary to prevent the formation of the red coloring matter, 
which would interfere with the delicacy of the reaction. 

Paper stained with a solution of this reagent, as well as with 
tetra-methyl-paraphenylen-diamine, has been introduced by Wurster 
as adelicate reagent for ozone. When moistened it turns blue with 
the smallest quantities of this active modification of oxygen. It 
also serves to detect substances which ozonize air, such as turpen- 
tine, colophony, etc. Hence, it is used to detect wood pulp in paper, 
during whose manufacture rosin is added tothe pulp. A moist 
strip of Wurster’s paper pressed upon such wood pulp paper turns 
blue. 

PREPARATION. From Helianthin (Orange III) as described in 
article on preparation of sulphanilic acid, on page 21. 

p Amido-benzol-azo-dimethyl-aniline, N He. Ce Ha. N:N. Ce Ha. N 
(C Hs)2. Used for the detection of nitrous acid,with which it forms 
a tetrazo salt, whose dilute solution turns blue on exposure to air 
(Meldola). 

NOTE. For other derivatives of Aniline and its homologues, 
see the articles as they occur in alphabetical order, and especially 
those in the chapter on Color Reagents and Indicators. 





ANTHRAQUINONE, Ce Ha (C O)2 Co Ha. 


Usrs. To detect the presence of small quantities of water in 
alcohol, ete. (Claus). A few milligrammes of anthraquinone and 


ANTIPYRINE. 44 


sodium amalgam are mixed and thoroughly shaken up with abso- 
lute ether (being absolutely free from alcohol and moisture). A 
few drops of the liquid to be tested for water are then added. If 
water be present a red color is produced. Absolute alcohol (which 
may be added without ether being used) produces a green color. 
Both colors disappear on shaking with air, but reappear again on 
standing quietly. 

Tests. Anthraquinone forms yellow, rhombic, needle-shaped 
crystals, melting at 278° C. and subliming at a higher temperature 
without residue. The commercial article is produced on the large 
scale by oxidation of anthracene, asa step in the manufacture of 
artific‘al alizarine, and is sufficiently pure for the above reaction. 

PREPARATION. On the small scale, it may be made by passing 
chlorine (or bromine) into a boiling solution of one part of anthra- 
cene in 6 parts of strong alcohol. After cooling, the precipitate is 
first washed on a filter with cold alcohol, then with dilute solution 
of sodium hydrate in water, then dried and sublimed in a glass 
tube. , 


ANTIPYRINE, Cu Hiz Ne O. 
Dimethyl-oxy-chinizine. 


Usss. To detect free nitrous acid (in amyl nitrite, ethyl nitrite, 
etc.) by the production of a deep emerald green color. A solution 
of antipyrine in water is added to this substance. If free nitrous 
acid is presenta deep green color at once results, followed by the 
deposition of green crystals of iso-nitroso-antipyrine, Cu Hn Ng Os. 
These are insoluble in water, soluble in alcohol, acetic acid and in 
alkaline hydrates. An excess of nitrous acid or nitric acid oxidizes 
the green salt and colors it red. 

By using a mixture of strictly neutralized sodium nitrite and 
antipyrine solutions, the presence of any free acid capable of liber- 
ating nitrous acid may be detected by the same reaction. 

With ferric salts antipyrine produces a red color similar to that 
of the sulphocyanides, but the reaction is not so delicate in great 
dilutions. 

Tests. Antipyrine, as sold by dealers, is sufficiently pure for use 
as areagent. It forms a white crystalline powder, melting at 113° 
C., soluble in two-thirds its weight of water. The solution is neu- 
tral to test papers. When mixed with some potassium or sodium 
nitrite and a few drops of sulphuric acid it must promptly turn 
green. It must be carefully preserved in the dark, as exposure im- 
pairs its activity. 

PREPARATION. The process of manufacture patented by Dr. 
Knorr consists in the production of methyl-oxy-chinizine, by the 


ARSENIC, 45 


condensation of equal molecules of phényl-hydrazine and aceto- 
acetic ester. This is heated at100 C. in closely sealed vessels with 
an equal amount of methyl alcohol and methyl iodide, and thus an 
impure icdide of the dimethyl compound results. This is purified 
by treatment with sulphur dioxide, and then the base is separated 
by sodium hydrate ard purified by recrystallization from toluol, 
ether or benzol. The solution is only made when needed, and then 
1 part of antipyrine is dissolved in ten parts of pure water. 


ARSENIC TRIOXIDE, Asz Os. 
Arsenous Acid Anhydride. 


Usrs. Arsenic trioxide serves to detect acetic acid in presence of 
other volatile organic acids by the kakodyl test. When an alka- 
line acetate is fused with Ase Os the very characteristic, disagree- 
able odor of dimethyl-arsine (kakodyl) is produced. It is also 
occasionally used as areducing agent to convert nitro-benzol into 
aniline, etc. Also for the preparation of decinormal volumetric so- 
lution of ‘sodium arsenite, used in the titration of chlorine, hypo- 
chlorites, bromine, iodine, ete. For the latter purpose the arsenic 
trioxide must be very pure. Mol. W. = 122.798. - 

Tests. Pure arsenic trioxide must completely volatilize when 
heated in a glass tube; the sublimate it then gives must be perfectly 
colorless or white, and must. not at first show a reddish color of 
the more easily sublimed sulphide, whose presence would render it 
unfit for volumetric use, as it rapidly changes the titre of the solu- 
tion by the formation of arsenicacid. The solution in water must 
not be colored dark by lead solution (absence of sulphide). It 
must give with ammoniated solution of silver nitrate a pure yellow 
precipitate (a brown red precipitate would indicate presence of 
arsenic acid). Its aqueous solution, acidulated with pure hydro- 
chloric acid, must give with hydrogen sulphide a pure yellow pre- 
cipitate. When converted into arsenetted hydrogen in a Marsh 
apparatus, the spots produced by the ignited gas on porcelain 
must completely dissolve in sodium hypochlorite, showing the ab- 
sence of antimony. 

In the powdered arsenic of commerce, the absence of chlorides 
may be shown by converting the trioxide into arsenic acid by 
means of boiling with concentrated nitric acid, diluting and then 
adding silver nitrate, when a white precipitate, soluble in ammonia, 
will indicate chlorine. 

Ammonium salts are said to be occasionally present, and may be 
detected by heating with sodium hydrate. 


t 


46 ASBESTUS. 


PREPARATION. From the white arsenic of commerce arsenic tri- 
oxide may generally be obtained of great purity by breaking open 
the larger pieces and carefully selecting the glassy transparent 
amorphous inner portions, rejecting the opaque, porcelain-like 
crystalline crust. The glassy amorphous modification is much 
more soluble in water than the crystalline opaque envelope. It is 
tested for purity, and, if found pure, is preserved in glass stop- 
pered bottles. It will soon become covered by an opaque crust, 
but this will not interfere with its use when it has once been fourd 
pure. 

ASBESTUS, AMIANTHUS. 


Usses. Asbestus is a natural silicate of calcium and magnesium, 
closely allied to hornblende; its purest variety is called amianthus. 
It occurs in slender, flax-like fibres, capable of resisting high tem- 
peratures without fusing, and is not attacked by water and most of 
the acids. This makes it valuable material for filtering many sub- 
stances which would destroy ordinary filtering paper. It is also 
used to close tubes, etc., in such manner that gases can easily pass 
through its interstices while powdered solids are retained. Some- 
times it is impregnated with concentrated sulphuric acid and 
placed into tubes to dry the passing gases. Occasionally it is 
coated with a finely divided metal, and thus used in either gas 
analysis or in the combustions of organic ultimate analysis. The 
long fibre is used as a support in blowpipe operations in the place 
of platinum wire. It is also woven into cloth, useful for various 
purposes. 

Tests. The purest, variety, amianthus, is preferable for most 
purposes, whether requiring long or short fibre. It must not yield 
anything soluble to either hot or cold water or hydrochloric acid. 
After boiling for some time with concentrated hydrochloric acid, 
this, on evaporation upon platinum foil, must show no residue. 
It must resist the temperature of white heat without fusion. 


PREPARATION. Asbestus of a less degree of purity may be used 
after having been deprived of all soluble matter by boiling with 
hydrochloric acid and thorough washing. Palladiwm-asbestus is 
made by dissolving 1 gramme of palladium in nitro-muriatic acid, 
and evaporating the solution until all free acid is expelled. The 
palladious chloride (about 1.7 gr.) is dissolved in very little water, 
and to this are added 5 Cc. of a cold, saturated, aqueous solution 
of sodium formate and enough pure sodium carbonate to render the 
liquid alkaline. 

With this mixture one gramme of pure, long-fibred amianthus is 
impregnated and dried; first at a very gentle heat, lastly at 100 C. 


ASSAY REAGENTS—AZOLITMIN. 47 
The palladium, reduced to a fine metallic state, is precipitated 
upon the fibre, and after being perfectly dried adheres well. It is 
washed with warm water upon a funnel until all soluble salts are 
removed, then again dried at 100° C., and carefully preserved with- 
out bending or unnecessary handling, in glass tubes. Itis used to 
absorb hydrogen from gas mixtures, etc. 

Platinum-Asbestus is prepared in the same manner, using for 1 
gramme of asbestus 1.2 gr. of platinic chloride, corresponding to 
about 0.5 gr. of metal. 

Copper- Asbestus is made by impregnating the short-fibred va- 
riety with saturated solution of pure copper nitrate, drying and 
heating to redness, when the salt will be converted into black 
cupric oxide. Itis then heated in a current of hydrogen gas until 
the oxide is fully reduced to metal. In the elementary analysis of 
organic substances containing nitrogen this is used instead of 
copper turnings. 


NOTE. Many other silicates, natural and artificial, are em- 
ployed for the same purposes as asbestus. Thus, pumice stone is 
used for soaking with sulphuric acid to dehydrate gases; it is also 
coated with metallic copper for organic analysis. Garnets, quartz 
in small fragments, kieselguhr, glass wool and slag wool are used 
for filtering acids. 


ASSAY REAGENTS, 


also called docimastic or pyrognostic reagents, are used in the assay 
of ores, etc.,in the dry way, by blowpipe or furnace operations. 
They are described under their respective titles. See Stlicie Acid, 
Coal, Fluxes, Lead, Lead Monoxide, Sodiwm Drborate, etc. 


AZOLITMIN. 


Uses. Azolitmin, being the most important of the four coloring 
principles contained in litmus, is sometimes isolated to serve-as 
indicator in alkalimetry and for the preparation of test papers. 
The removal of the other coloring principles, which interfere with 
its prompt reaction, makes it more sensitive than the crude litmus 
preparation. Itis colored red by acids, blue by alkalies. 

Tests. Azolitmin forms an amorphous, red-brown powder, very 
little soluble in water, insoluble in acids, forming with alkalies 
blue salts, which easily dissolve in water. 

PREPARATION. Litmus is digested with 6 parts of hot water; the 
solution is filtered, and into it strips of cotton or linen cloth (free 
from starch) are immersed until the color has been absorbed. They 
are then taken out, permitted to drip and, when partly dry, are 
immersed into dilute sulphuric acid (1%). The acid renders the 


, 


48 BARIUM COMPOUNDS. 


azolitmin red and insoluble, and fixes it in the fibre. The strips are 
next washed in water until no more coloring matter can be ex- 
tracted. ‘This removes the other pigments and leaves only azolit- 
min in the cloth. It is next soaked in water made alkaline by a 
small quantity of sodium hydrate. The blue, soluble sodium salt is 
formed, and may be extracted by pressure. From this solution 
either the dry azolitmin is obtained by precipitation with sulphuric 
acid, or the solution is mixed with only afew drops of very dilute 
acid to give it a neutral purple tint, and then preserved as an indi- 
cator for alkalimetrie work, or converted into test paper by soak- 
ing strips of unsized paper with it. See also Color Reagents and 
Indicators, Litmus and Testpapers. 


BARIUM COMPOUNDS. 


BARIUM ACETATE, Ba (C2Hs O2)2 + He O. 


Usrs. To remove sulphuric acid by precipitation as barium sul- 
phate in cases where the introduction of acetic acid is preferable to 
that of the other acids of barium salts. Hence, it isemployed in the 
separation of magnesium from the alkalies (in water analysis, etc.). 
The sulphates of magnesium and the alkalies are converted into 
acetates, and these, by ignition, into carbonates. Water dissolves 
out the alkalies and leaves magnesium carbonate and oxide. 

Tests. As the reagent is but seldom used, it is best to prepare it, 
whenever needed, from pure materials. When bought in crystals 
it should, in addition to the tests used for other barium salts (see 
barium chloride), show the absence of hydrochloric, nitric and 
other acids. Its solution is therefore precipitated by dilute, pure 
sulphuric acid in slight excess and filtered. The filtrate must leave 
no residue when heated on platinum foil. It must give no precipi- 
tate with silver nitrate either before or after neutralization with 
sodium hydrate. With diphenyl-amine and concentrated sulphuric 
acid it must show no blue color. 

PREPARATION. Pure barium carbonate is added in slight excess 
to pure dilute acetic acid. After standing some time, the solution 
is filtered and is then ready for use. By evaporation crystals may 
be obtained, which are dissolved in 7.2 parts of water, when needed 
in solution. 


BARIUM CARBONATE, Ba COs, 


Usrs. Native barium carbonate, witherite, is too impure for ana- 
lytical purposes, but is often used to prepare from it pure barium 


BARIUM CHLORIDE. 49 


chloride and other salts. The pure salt is used to remove by pre- 
cipitation ferric, chromic and aluminium salts from those of zinc, 
manganese and other bases of the third and fourth analytical 
groups, sulphuric acid being absent. Also to remove sulphuric 
acid from solutions, etc. Also to prepare some of the less fre 
quently used barium salts, such as the acetate, by saturating their 
acids. 

Tests. Barium carbonate must yield nothing to pure water de- 
prived of carbonic acid gas by boiling. It must leave no residue 
insoluble in water after neutralization with pure dilute hydro- 
chloric acid. On addition of a slight excess of pure dilute sulphuric 
acid to this solution, the whole of the base must be precipitated as 
barium sulphate, and after boiling and careful filtration, so that 
none of the fine particles of the precipitate can pass through the 
filter, addition of alcohol must not produce a turbidity (absence of 
calcium and strontium), nor leave any residue on heating upon 
platinum foil. 

PREPARATION. To a boiling solution of pure, crystallized barium 
chloride in pure water add a concentrated solution of pure am- 
monium carbonate, mixed with a little ammonia water, as long as 
a precipitate falls. Wash out, first by repeated decantation, then 
on a filter, until every trace of chloride is removed, as shown by 
nitrate of silver. The precipitate is then dried and preserved free 
from dust, etc. For use it is mixed with pure water to the con- 
sistence of thick milk. 


BARIUM CHLORIDE, Ba Cle-+ 2H: O. 


Uses. To detect and separate the inorganic acids of the first 
group, which form barium salts insoluble in water, from those of 
the other groups forming soluble barium salts. As a special re- 
agent for sulphuric acid, whose barium salt is insoluble in water 
and in all dilute acids, but soluble in hot concentrated sulphuric 
acid as barium disulphate, Ba(HS O4)2. Also in volumetric ana- 
lysis as normal and decinormal solution. Ba Cle + 2H2 O = 248.428. 

Tests. The pure salt forms colorless, rhombic crystals, soluble 
in 2.3 parts of water at 15° C., insoluble in absolute alcohol, and in 
concentrated H Cl. The aqueous solution must be strictly neutral 
to test papers; must not yield any precipitate with hydrogen sul- 
phide, or ammonium sulphide, containing nofree ammonia. After 
precipitation with sulphuric acid in slight excess the filtrate must 
yield no precipitate with sodium carbonate and hydrate, nor leave 
any permanent residue on heating upon platinum foil. 

To the flame it must communicate a yellowish-green color, free 
from red, showing a pure barium spectrum. To render the flame 


50 BARIUM DIOXIDE. 


test more effective, the salt is washed with alcohol of spec. gr. 0.928 
and the washings tested, in which very little barium chloride dis- 
solves, while the calcium and strontium salts, if present, are freely 
dissolved and thus more readily shown. 

PREPARATION. There are two native minerals which serve as the 
source of barium preparations, the sulphate, called heavy spar or 
barytes, and the carbonate or witherite. On the larger scale, finely 
powdered barium sulphate is heated to a white heat with chareoal 
and manganous chloride (obtained as a bye-product in the chlorine 
manufacture). Or by heating together 12 parts of heavy spar, 6 
parts of dry calcium chloride, 2 parts of charcoal and 2 parts of iron. 
The product in each case is leached out with boiling water, crystal- 
lized and refined by recrystallization. 

On the smaller scale, 8 parts of finely powdered barium sulphate 
are mixed thoroughly with two parts of lampblack, and one part of 
linseed oil (or rosin), placed ina crucible and gradually heated up 
to a bright white heat, at which they are kept for many hours. 
The product, consisting of impure barium sulphide, is leached out 
with about four times its weight of water. Of the solution about 
1-20th part is set aside, and to the rest a slight excess of hydro- 
chloric acid is added. After the expulsion of the HS, the liquid is 
filtered, evaporated to about one-third, and then enough of the re- 
served barium sulphide solution is added to render the liquid 
slightly alkaline. It is now again filtered, evaporated to dryness, 
dissolved in three parts of water, filtered and, after slight acidula- 
tion with hydrochloric acid, concentrated and crystallized. The 
crystals are dissolved in 2 parts of hot water and 2 parts of alcohol 
added. This precipitates barium chloride, which is separated on a 
filter and washed with alcohol, while strontium and calcium chlor- 
ides remain in solution. 

From witherite, barium chloride is made by dissolving 10 parts 
of the powdered material in about 15 parts of hydrochloric acid. 
After solution, 1 more part of witherite is added and digested in a 
warm place for 24 hours. In case iron is present, as shown by 
tannic acid and other reagents, enough of the solution of bleach- 
ing powder (calcium hypochlorite) is added to remove it. The 
liquid is then filtered, evaporated, crystallized, and after reerystal- 
lization, purified by precipitating with alcohol as above. 

For use, 1 part of the crystals is dissolved in ten parts of water. 

Normal solution contains 243.423 grammes in 1 litre. 


BARIUM DIOXIDE, Ba Oz. 


Usses. To prepare hydrogen dioxide for detection of chromie 
acid, titanic acid, etc. © 


BARIUM HYDRATE. 51 


Tests. After precipitation by sulphuric acid the filtrate must on 
evaporation leave no fixed residue. When a small quantity is sus- 
pended in cold water and dilute hydrochloric acid added, it must 
yield sufficient hydrogen dioxide to color blue a dilute solution of 
potassium dichromate. 

PREPARATION. As pure dioxide is somewhat difficult to obtain 
entirely free from oxide, and as the presence of this does not 
interfere with the use, a preparation of suflicient purity is obtained 
by heating dry barium oxide, Ba O, to a red heat in a suitable tube, 
while a current of oxygen is passing over it. 


BARIUM HYDRATE, Ba (O H)e. 
(Crystallized : Ba (O H)2 + 8H: O.) 


Uses. In the dry state it is used as a flux to decompose silicates 
for the determination of their alkalies. In crystals and in solution 
it serves to remove C Oz from mixed gases ; to prepare pure alka- 
line hydrates ; to liberate organic and inorganic bases from their 
compounds, e. g., glycerin from fats ; to remove chlorophyll, ete. 
To precipitate acids forming insoluble barium salts, e. g., to re- 
move sulphates, phosphates, etc., from urine, preparatory to test- 
ing for urea, etc. In volumetric analysis for acidimetry, determi- 
nation of chloral hydrate, etc. Molec. weight: Ba (O H)z = 170.683; 
Ba (O H)e + 8He2 O = 314.363, 

Tests. After precipitation by sulphuric acid the filtrate must 
leave no fixed residue on evaporation. The salt Ba (O H)z + 8H2 O 
is soluble at 15° C. in 20 parts of water, at 100° C. in 8 parts. 

PREPARATION, Either by precipitation of a concentrated solu- 
tion of barium chloride by sodium hydrate, or by heating barium 
nitrate for some time to a white heat and then adding water. Or 
better, by heating a mixture of 10 parts of barium carbonate with 1 
part of lampblack, and 1 part of linseed oil (or rosin) for several 
days to a white heat (by placing the crucible in a brick kiln). The 
cooled mass is leached out with boiling water, filtered while hot, 
and the clear solution left to cool in well-stoppered bottles, so as 
to let the crystals deposit. They are separated by filtration and 
kept in well-closed bottles. In all of these operations access of 
air must be prevented as much as possible, so as to exclude its 
C Oe from the solution, which would rapidly absorbit. From the 
crystals, the dry barium hydrate is obtained by heating them ina 
platinum or silver vessel till the water of crystallization is expelled, 
which occurs below a red heat. 

Baryta Water. For use,1 part of the crystals is dissolved in 20 
parts of water, boiled immediately before, so as to expel C Oz. The 


52 BARIUM MERCURIC IODIDE—NITRATE—SULPHIDE. 


volumetric solution is made of half-normal strength, 157.181 
grammes to 1 litre, containing 85.341 gr. of Ba(O H)2. To prevent 
its rapid deterioration a special absorption tube is attached to the 
bottle, a layer of petroleum is poured upon its surface, and fre- 
quently the burette is connected with the containing vessel so as to 
exclude C Ox. 


BARIUM MERCURIC IODIDE, Ba le Hg le. 
Rohrbach’s Solution. 


Uses. In petrographic work the concentrated solution is used to 
separate various components of rocks by difference in specific 
gravity. Thesolution in its utmost concentration contains an ex- 
cess of mercuric iodide and attains the spec. gray. 3.588, but be- 
comes gradually lighter by the separation of crystals of mercuric 
iodide. Epidote and olivine float in it. 

PREPARATION. Into a small flask place 100 grammes barium 
iodide (which may be made from barium carbonate and hydriodic 
acid), 180 gr. red mercuric iodide and 20 Ce. of water. Heat to 200° 
C. on an oil bath, accelerating the solution by agitation. As soon 
as dissolved, reduce the temperature to 100° and evaporate (in a 
porcelain dish) until a crystal of epidote floats. On cooling, the 
density increases. The solution is carefully decanted and pre- 
served in a glass-stoppered vial. 

For other petrographic reagents, see Bromoform, Cadmium Boro- 
tungstate and Mercuric Potassium Iodide. 


BARIUM NITRATE, Ba (N O3)2. 


Usrs. For the same purposes as barium chloride, when the intro- 
duction of chlorine is objectionable. By ignition it loses its acid 
and is converted into BaO. Mol. W. = 260.565. 

Tests. It crystallizes in regular octahedra, soluble in 12 parts of 
water, insoluble in alcohol. In addition to the tests for other ba- 
rium salts, the absence of chlorine must be shown by silver nitrate 
failing to give a precipitate in a dilute solution, slightly acidulated 
with nitric acid. 

PREPARATION. Barium carbonate is saturated with dilute nitric 
acid, concentrated and crystallized. 

For use, dissolve 1 part in 15 parts of water. 


BARIUM SULPHIDE, Ba S. 


Usep for the convenient preparation of hydrogen sulphide free 
from arsenic (Winkler). The almost universal freedom from ar- 
senic of the native barium sulphate, from which the material is 
prepared, together with its cheapness, recommends it as a substitute 


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BENZIN. 53 


for ferrous sulphide. Itis used, broken into lumps, in any form of 
generating apparatus, and with pure acid furnishes pure hydrogen 
sulphide. 

PREPARATION. 100 parts of heavy spar, 25 parts of powdered 
charcoal and 20 parts of sodium chloride are intimately mixed, and 
by aid of.a little water formed into a stiff dough. This is pressed 
into clay crucibles of suitable size (about 25 Cm. high and 10 Cm. 
wide), and dried at a gentle heat. The crucibles are covered first 
with powdered charcoal, then the cover is luted on with clay, 
leaving asmall opening for escape of gas. They are then heated 
for several hours to a white heat (ina brick kiln or suitable fur- 
nace). After cooling, the crucibles are easily emptied, the sintered 
mass broken into lumps of suitable size and preserved in tightly 
sealed cans. When stone coal, absolutely free from arsenical 
pyrites, is used in the place of charcoal, a more compact mass is ob- 
tained. 


BENZIN. 


Petroleum-ether. 


Notr. The volatile fraction of petroleum boiling between 50° 
and 60° C., of spec. gr. 0.670 to 0.675, consisting principally of pen- 
tane, Cs Hiz, hexane, Ce Hu, and their isomers, is recognized in the 
U.S. P. under this name, while other authorities use the name for 
a different substance. The similarity of the name of the coaltar 
product, benzol, also called benzene, has led to some confusion. 
Dragendorff, who introduced the petroleum product into plant 
analysis, calls it petrolewm-ether, including in this designation all 
the more volatile congtituents, while he gives the name benzin to 
the coaltar derivative . Ce He. To prevent mistakes it is best 
to follow the nomenclature of the Pharmacopeeia, avoid the name 
benzene, and call the coaltar product BENZOL, as proposed by Lie- 
big in 1834), confining the names BENZIN and PETROLEUM-ETHER 
to the more volatile portion of petroleum, although, strictly 
speaking, it is no ether. 

Uses. In organic analysis benzin is used for dissolving resins, 
oils and fats ; the more volatile portions serve to remove the active 
principles of plants from various solutions. Thus, from acidulated 
solution petroleum-ether extracts salicylic acid, phenols, absinthin, 
piperine, lupuline, cantharidin, etc.; from alkaline solution strych- 
nine, brucine, emetine, coniine, nicotine, etc., etc. (Dragendorf,.) 

Tests. For solution of oils and fats the U. 8. P. benzinis suitable. 
On evaporation, it should not leave a disagreeable odor of sulphur 
compounds, nor any less volatile residue, boiling above 60° C. On 


54 BENZOL. 


agitating 2 parts of benzin with a mixture of four parts of nitric 
and one part of concentrated sulphuric acid, neither a dark color 
nor a bitter almond odor should be produced, the latter indicating 
presence of benzol, which occurs in small quantity in Russian pe- 
troleum. For extracting alkaloids, etc., a petroleum-ether of lower 
boiling point is preferable. 

PREPARATION. A sufficiently pure product, rectified on the 
large scale, is generally obtainable in the market. If necessary, 
commercial benzin may be refined by first digesting with a solution 
of potassium dichromate and sulphuric acid, washing and then 
mixing with about one-fourth of pure hogs lard. The mixture is 
carefully distilled, rejecting the portion boiling above 60° C., and, 
if necessary, redistilled. 


BENZOL, Ce He. 
(Benzene.) 


UsrEs. As a solvent of fats, oils, resins, caoutchouc, sulphur, 
phosphorus, iodine, alkaloids, ete. For the preparation of nitro- 
benzol, aniline and other derivatives. 

Tests. Pure benzol is a transparent liquid of spec. gr. 0.8846 at 
15°C. It boils at 80.387° C. and solidifies at 0° to rhombic prisms. 
A higher boiling point indicates the presence of toluol and other 
homologues of higher boiling point and lower spec. gravity. It is 
insoluble in water, soluble in 4 parts of aleohol. Pureconcentrated 
sulphuric acid dissolves pure benzol without coloration, forming 
benzol-sulphonie acid. Benzol should be free from more than 
traces of thiophene, C4 H4 S, which is pratt to the amount of 4% 
in crude benzol from coaltar. When a small amount of benzol con- 
taining thiophene is dropped on heated sodium, an alkaline sul- 
phide is formed, as shown by the violet-blue color produced by 
sodium nitroprusside in a solution of the charred residue. 

PREBARATION. The purest benzol is obtained by the dry distilla- 
tion of 1 part benzoic acid with three parts of slightly moistened 
quicklime and rectification by fractional distillation. On the large 
scale, benzol is made for the manufacture of aniline by distillation 
of coaltar. The so-called light oil, which comes over between 60° 
and 150° C., is agitated with sulphuric acid to remove basic com- 
pounds; it is then washed with weak lye, and rectified by repeated 
fractional distillation. The final product is cooled with ice and the 
benzol crystals, which form at 0°, are separated and drained. 


Benzo-purpurin, B, see color reagents and indicators, 


BISMUTH COMPOUNDS. 55 


BISMUTH COMPOUNDS. 


BISMUTH HYDRATE, Bi O (OH). 


Usres. To convert, by heating in alkaline solution, metallic sul- 
phides into their hydrates and oxides ; to convert arsenic trisul- 


phide into arsenite, the pentasulphide into arsenate. In most 
cases the subnitrate may be substituted for it. 


Tests. It must dissolve in nitric acid without residue, and with- 
out becoming colored blue (copper). The absence of tin, antimony, 
arsenic and tellurium is shown by dissolving the hydrate in dilute 
nitric acid, precipitating with He S and filtering. The precipitated 
bismuth sulphide is digested with ammonium sulphide, which 
should not extract anything soluble, so that when filtered and acid- 
ulated with H Cl only pure sulphur should be precipitated . 

In the first filtrate from the precipitate by HzS in acid solution 
thallium may be recognized by neutralizing and adding potas- 
slum iodide, which would precipitate yellow thallous iodide. Iron 
and other metals of the fourth group would be shown by neutraliz- 
ing with ammonia and adding ammonium sulphide. Silver, which 
is frequently present in bismuth compounds, is shown by precipi- 
tating the solution of bismuth hydrate in nitric acid with concen- 
trated H Cl, when bismuth will remain in solution, while silver 
chloride precipitates and is blackened by sunlight. Copper may 
be shown either by ammonia or in small quantities by electrolytic 
deposition. For arsenig Mleztmann’s test may be used (page 14). 

PREPARATION. To Masure bismuth hydrate (and other com- 
pounds) free from antimony, arsenic, tin, tellurium, silver, copper, 
thallium and iron, which, from being found in the bismuth ores, 
occasionally pass into the metal and the preparations made from it, 
itis best tostart from a pure metal. Commercial bismuth is first 
purified by remelting at lowest heat in a shallow iron pan, slightly 
inclined. Arsenic is thus almost entirely volatilized, while most 
other impurities remain unmelted on the pan, the purer bismuth 
trickling off. It is again melted, and for every 1,000 parts a mix- 
ture of 45 parts of potassium cyanide and 17 parts of sulphur is 
stirred in, while the heat isincreased. This converts the remain- 
ing arsenic, copper, etc., into sulphides, which separate from the 
melted bismuth. To free it from the last traces of impurities, the 
metal (or the commercial hydrate or subnitrate) is dissolved in 
nitric acid, avoiding excess. To the solution water is added until it 


4% 


56 BISMUTH-POTASSIUM IODIDE. 


begins to get turbid, the liquid is left at rest to deposit the precipi- 
tate. from which itis decanted. Sodium (or potassium) hydrate is 
now added till the reaction becomes alkaline, and then concen- 
trated glycerine, which redissolves the bismuth hydrate, but leaves 
other metals undissolved. To this solution there is then added a 
solution of 5 parts of glucose for one part of bismuth employed 
(freed from lime by addition of sodium carbonate) and the mixture 
left at rest in a well-closed flask, to reduce whatever silver and 
copper was present and deposit them as metallic silver and cuprous 
oxide. After filtration, bismuth is reduced by boiling and precipi- 
tates as a finely divided gray powder, absolutely pure from arsenic 
and other impurities. This is collected on a filter and washed. 

From the pure metal the hydrate.is prepared by dissolving it in 
nitric acid, precipitating by sodium hydrate, washing out and dry- 
ing. 

BISMUTH-POTASSIUM IODIDE, Bils. 3K I. 


Dragendorff’s Reagent. 


Uses, Inthe analysis of alkaloids this is used similarly to cad- 
mium-potassium iodide. The addition of a few drops of its solution 
to10 Ce. of an aqueous solution of alkaloids, acidulated with 2 Cc. of 
sulphuric acid, produces an amorphous orange precipitate with 
even very dilute solution of brucine, strychnine, curarine, atropine, 
physostigmine, aconitine, quinine, cinchonine, morphine, codeine, 
narcotine, papaverine, thebaine, delphinine, caffeine, berberine, 
bebeerine, nicotine and coniine. Narceine, theobromine, veratrine, 
digitaline and solanine are precipitated from concentrated solution, 
dilute solutions become only slightly turbid. Ammonia and alka- 
line hydrates and carbonates decomposéjhe reagent to bismuth 
hydrate or carbonate. Urea, uric acid, hippuric acid, asparagin, 
creatine and creatinine are not precipitated. (Dragendorf.) 

PREPARATION. Bismuth iodide is first prepared by subliming in 
a tube of hard Bohemian glass an intimate mixture of 4 parts of 
metallic bismuth (or 5 parts of bismuth sulphide) with 7 parts of 
iodine. The sublimate is dissolved in a warm, concentrated solu- 
tion of potassium iodide, and as much more of this is added as was 
necessary for solution. The reagent is kept in the dark in well- 
closed bottles. It will not keep after dilution. 

Fron’s modification of Dragendorff’s solution requires acidulat- 
ing the alkaloid solution with strong H Cl, to prevent decomposi- 
tion of the reagent. It is made by suspending 1.5 gr. of freshly 
precipitated bismuth subnitrate in 20 Cc. of water, heating to boil- 
ing and and adding 7 grammes of potassium iodide and 10 Ce. of 
H Cl. 


BISMUTH SODIUM HYPOSULPHITE—SUBNITRATE—TETROXIDE, 54 


BISMUTH-SODIUM HYPOSULPHITE. 
( Throsulphate.) 


Usrs. To detect potassium whose salts are precipitated by the 
reagent as bismuth-potassium hyposulphite, of lemon-yellow color, 
entirely insoluble in alcohol. (Campari.) 


PREPARATION. The reagent is only prepared when needed by 
dissolving bismuth subnitrate in as little H Cl as possible; sodium 
hyposulphite (thiosulphate) is at the same time dissolved in a mini- 
mum of water. Two or three drops of each solution are then 
mixed and added to 5 Ce. of strong alcohol. The colorless mixture 
produces the yellow precipitate in potassium salts. 


BISMUTH SUBNITRATE, Bi O N Os + H2 O. 


Uses. For detection of glucose in urine, either by Boettger’s 
method (adding the bismuth salt and sodium bicarbonate to the 
urine and heating), or by some of its modifications, in which an 
alkaline solution of bismuth is prepared from it. Among these, 
Nylander’s solution appears to be most satisfactory. Also, in the 
same manner as bismuth hydrate, in converting arsenic sulphides 
into the corresponding oxides. Also for preparing other bismuth 
compounds. 

Tests. It should conform to the tests for absence of foreign sub- 
stances enumerated under bismuth hydrate. Especially should 
freedom from arsenic be shown by Fleitmann’s test (see Nitric Acid, 
page 14). 

PREPARATION. Dissolve 1 part of pure, granulated bismuth in 6 
parts of pure nitric acid of spec. gray. 1.25; apply heat enough to- 
ward the last (to finish ‘the solution) to expel the red fumes and to 
reduce the volume to about one-third. Then pour into a large 
amount of pure water. Decant the acid liquid from the subsided 
precipitate, add more water and decant again several times, finally 
drain the precipitate and dry it ata gentle heat. Ifit should give 
off nitrous fumes it must be washed again. 

Nylander’s Solution is made by dissolving 2 gr. bismuth subni- 
trate and 4 gr. rochelle salt in a solution of 10 gr. sodium hydrate in 
90 Ce. water, and separating the undissolved bismuth salt ; one 
Ce. of this solution is added to 10 Ce. of urine or other saccha- 
rine liquid. 


BISMUTH TETROXIDE, 2(Biz 04). He O. 


Ussrs. For volumetric determination of manganese. It converts, 
in connection with nitric acid, the lower oxides of manganese into 


58 BRAZILWOOD. d 
permanganic acid, which may then be volumetrically determined 
by oxalic acid (Leop. Schneider). 

PREPARATION. One part eachof bismuth hydrate and potassium 
chlorate are intimately mixed and heated to redness. The mixture 
is then fused with two parts of sodium hydrate. The dark brown 
mass is washed out with water until it shows no more alkaline re- 
action, leaving a pale brown residue of sodium bismuthate, Na Bi 
Os. This is triturated with dilute (5%) nitric acid, which dissolves 
out the sodium, evolves oxygen and leaves the red-brown hydrate 
of the tetroxide, which is washed and dried. 


Black Flux, see Fluxes. 
Bohlig’s Reagent, see Mercuric Oxychloride. 
Borax, see Sodium Didorate. 


BRASS. 


In the shape of foil, wire or turnings, brass is sometimes substi- 
tuted for copper, zinc or gold to precipitate mercury from its salts; 
brass foil is used in Hager’s Kramato-method for detection of ar- 
senic. 


BRAZILWOOD. 


Pernambuco wood. 


Usgs. To detect hydrofluoric acid and mineral acids in vinegar. 
The brazilwood and the closely allied sappanwood, both derived 
from varieties of czesalpinia, contain a crystallizable yellow color- 
ing principle, Brazilin, C2 Ha» O7, which, on exposure to light, 
changes to a reddish color. With sulphuric, nitric and hydro- 
chloric acid it forms compounds of an intense peachbloom-red 
color. Hydrofluoric acid and many organic acids produce with it 
a bright yellow. 

It is generally employed as a testpaper, made by immersing strips 
of unsized paper in a strong watery infusion of the wood. It must 
be prepared, dried and preserved with exclusion of daylight. 

When a strip of moist brazilwood paper, slightly reddened by 
exposure to light, is exposed to the fumes of hydrofluoric acid it 
turns yellow. This serves especially in the blowpipe test of mine- 
rals containing fluorides, which are decomposed by microcosmic 
salt. 

When brazilwood paper is immersed for half a minute in vinegar 
(or other liquids), containing even less than one-half per cent of 
sulphuric acid, and then dried, the color becomes a bright peach- 
bloom-red. Hydrochloric or nitric acid produce a similar effect. 


BROMINE. 59 


BROMINE, Br. 


Atomic weight = 79.768. 


Usgs. Bromine, being characterized by great affinity for hydro- 
gen and for metals, serves, therefore, as an oxidizer, and for the 
conversion of metals into bromides, most of which are soluble in 
water. It sets free iodine from its compounds; it readily unites 
with ‘sulphur, thus serving for the decomposition of sulphides; it 
liberates nitrogen from ammonia; it forms with phenol an insol- 
uble tribromphenol, and thus is used for its detection and volumetric 
determination (Koppeschaar). In combination with alkalies (as 
hypobromite) it serves to decompose urea and to determine its 
quantity by measuring the resulting nitrogen (Knop and Huefner). 
In solution in water, hydrochloric acid or potassium bromide solu- 
tion, it is useful for detection of alkaloids, being used instead of 
chlorine to produce the thalleioquine reaction with quinine and 
quinidine; also to precipitate cinchonidine, oxyacanthine, sanguin- 
arine, hydrastine, bebeerine, etc. With bile colors it produces the 
characteristic color reactions. It is also used in the solid form, by 
impregnating cylinders formed of the silicious earth, called Kiesel- 
guhr (or, improperly, infusorial earth) in mineral assays, for the 
decomposition of natural metallic sulphides. (A. Brand.) 

Tests. At ordinary temperatures,pure bromine is a dark brown- 
red liquid, emitting orange-red vapors. At 15° C.its spec. grav. is 
2.97; at —24.5° C. it becomes solid, and boils at 63° C. under normal 
pressure of 760 Mm. At 15° C. it dissolves in 33.3 parts of water, 
forming bromine water, which must be preserved in the dark, as in 
sunlight it is rapidly decomposed, forming oxygen and hydro- 
bromic acid; potassium bromide, as well as hydrochloric acid, in- 
creases its solubility. It also dissolves in alcohol, ether, chloro- 
form, etc., but gradually decomposes them, as well as cork, caout- 
chouc, etc. 

Commercial bromine is seldom entirely free from chlorine and 
bromoform, but these may be disregarded in most operations, if 
not present in too large a quantity. To detect chlorine, the bro- 
mine is converted into barium bromide by neutralizing with pure 
baryta water, crystallizing the resultant mixture of barium bromate 
and bromide and heating the crystals to redness. The resulting 
barium bromide is entirely soluble in absolute alcohol, barium 
chloride being left as insoluble residue. 

Absence of iodine may be shown by shaking an aqueous solution 
of bromine with ferric chloride and chloroform. Iodine would 
color the chloroform violet. When dissolved in solution of sodium 
hydrate no yellow drops should separate, nor any odor of bromo- 
form be given off. 


60 BROMOFORM—BRUCINE. 


PREPARATION. Pure bromine may be made from the crude com- 
mercial article by repeated redistillation over powdered potassium 
bromide, rejecting the last portions of the distillate. The organic 
matter is entirely destroyed by passing the vapor over red hot 
manganese dioxide. It may be made absolutely pure by convert- 
ing the bromine into barium bromide by high heat, dissolving in 
absolute alcohol and, after removal of the alcohol, distilling the 
pure salt with pure sulphuric acid and manganese dioxide. 

Deci-normal solution of bromine is made by mixing 100 Cc. of 
deci-normal solution of potassium bromide, containing 11.8787 gr. 
K Br in one litre, with 100 Cc. of deci-normal potassium bromate 
solution, containing 16.6667 gr. K Br Ogin one litre, and with 10 Ce. 
of pure sulphuric acid. It contains 7.9768 gr. Br in one litre, but 
will rapidly decompose in the light. Paper dipped into a solution of 
starch and zinc iodide serves as indicator. It is employed for titra- 
tion of phenol. 


BROMOFORM, CH Brs. 


UsED occasionally in petrographic work for mechanical separa- 
tion of the ingredients of rocks by specific gravity. For this pur- 
pose the commercial article of spec. gr. 2.775 at 14.5 C. is of sufli- 
cient purity. Itis often obtained as a bye-product of the bromine 
manufacture. 

For other petrographic reagents see Bariwm Mercuric Iodide, 
Cadmium Boro-tungstate and Mercuric Potassium Iodide. 


BRUCINE, Ces Has Ne O4 + 2He O. 


Uses. For the detection and approximate estimation of small 
quantities of nitric acid and nitrates, especially in drinking water. 
With nitric acid brucine produces an intense red eolor, rapidly 
changing to yellow (Kakoteline). Itis used by adding to the water 
to be examined an equal bulk of a solution of 1 part of brucine in 
300 parts of very dilute sulphuric acid. To this concentrated sul- 
phuric acid is cautiously poured, so as to form a layer underneath. 
The red color appears at the zone of contact. Molec. Weight = 
465.05. 

Tests. The commercial article is sufficiently pure. As it is ob- 
tained as a bye-product of the manufacture of strychnine, it may 
contain small amounts of other strychnos alkaloids, but they do 
not interfere with its use. It forms white, monoclinic crystals, sol- 
uble at 15° C. in 320 parts of water, 1.5 parts of alcohol and in 7 
parts of chloroform. 


CADMIUM COMPOUNDS—IODIDK. 61 


CADMIUM COMPOUNDS. 


CADMIUM BORO-TUNGSTATE, Bie He We Os) . 7(W Os). Be Os + 
16 He O. 


Klein’s Reagent. 


Uses. For separations in petrographic work. A saturated 
aqueous solution of this salt has, at 15° C., spec. gr. 3.28. Crystals 
fuse at 75°C. in their water of crystallization, and this liquid has 
spec. gr. 3.6, and is sufficiently dense to float crystals of spinel. 

PREPARATION. Six parts of sodium tungstate are dissolved in 30 
parts of water and boiled with 9 parts of boracic acid. The solu- 
tion is stirred while cooling and decanted from the crystals of 
borax, which separate. It is concentrated by evaporation and 
crystals removed as they form, until it becomes dense enough to 
float the glass stirring rod. Two parts of barium chloride, dissolved 
in a minimum of boiling water, are now added to the boiling solu- 
tion. A dense white precipitate is formed, which is separated by 
filtration and washed with water. It is then dissolved in hot 
water containing 10% of concentrated hydrochloric acid. To the 
solution some more hydrochloric acid is added, and it is then evapo- 
rated to dryness. The dry mass is dissolved in boiling water, leav- 
ing an insoluble residue of tungstic acid. From the hot concen- 
trated solution quadratic crystals of bariwm borotungstate, 2(Ba He 
W2 Os) .'7(W Os). B2O3 + 16H2O, form on cooling, and may be puri- 
fied by recrystallization. To a boiling solution of the crystals a 
concentrated solution of cadmium sulphate is now added as long as 
barium sulphate precipitates. The liquid is filtered, and from it 
erystals of cadmium boro-tungstate are obtained by evaporation on 
a water bath. The salt is soluble in less than one-tenth of its 
weight of water. 

It is used in a Harada’s separating funnel, surrounded with a hot 
water jacket. 


CADMIUM IODIDE, Cd k:. 


Uses. To add to starch solution for the purpose of indicating the 
presence of chlorine, bromine, nitrous acid or other agents capable 
of liberating iodine from its compounds. It is preferred for this 
purpose to potassium or zinc iodide, on account ofits greater sta- 
bility and resistance to decomposition by light, etc., although it is 
not entirely unaffected by strong sunlight. 


62 CADMIUM POTASSIUM IODIDE—CALCIUM COMPOUNDS. 


Tests. The saltforms hexagonal plates of a white, pearly lustre, 
soluble in alcohol. At 20° C. one part requires 1.1 of water for so- 
lution. After protracted exposure to light Cd Iz becomes yellow, 
and should then be rejected until purified again. Its aqueous solu- 
tion, slightly acidulated with H Cland saturated with He S, should 
yield a pure yellow precipitate. The filtrate from this should, on 
evaporation, leave no permanent residue. 

PREPARATION. Digest one part of pure metallic cadmium, in fine 
granules, with 2 parts of pure powdered iodine, suspended in 4 
parts of water. After the solution has become colorless, filter it off 
from the small excess of cadmium, evaporate and set aside to crys- 
tallize. 

Molec. weight = 364.884; Cd = 111.77; I = 126.557. 


CADMIUM POTASSIUM IODIDE, Cd Iz. 2K I + 2H20, 


Marme'’s Reagent. 


Usrs. The solution of this salt produces in solutions of a great 
number of alkaloids, acidulated with H2SOu., floceculent precipi- 
tates, some of which soon become crystalline (nicotine, morphine, 
cinchonidine, etc.). They are easily soluble in alcohol and in an 
excess of the reagent; less so in water, insoluble in ether. From 
the precipitates the pure alkaloids are easily obtained by mixing 
them with solutions of alkaline hydrates or carbonates, and shak- 
ing out the free alkaloid with amyl alcohol, ether or benzol. 

Strychnine and quinine are precipitated completely from solu- 
tions of 1:10000, and many other alkaloids (of opium, cinchona, 
strychnos, etc., etc.) in almost as great dilution; while the reagent 
fails to precipitate glucosides (such as salicin, amygdalin, digitalin, 
etc.), urea and ureides, caffeine, etc. (Marmé.) 

PREPARATION. A concentrated solution of K I is divided into 2 
equal parts. One of them is heated to boiling and cadmium iodide 
is added to it as long asit will dissolve. The other portion of K I 
solution is then added, and by concentration crystals of 
Cd Iz. 2K I+ 2H: O are obtained. A saturated solution may be 
preserved for a long time, while in dilution it rapidly decomposes 


CALCIUM COMPOUNDS. 
Calcium Carbonate, Ca COs. 


Usrs. In assaying for iron or copper as a flux. The ordinary 
crystallized calcite is sufficiently pure. 


CALCIUM CHLORIDE. 63 


CALCIUM CHLORIDE, Ca Cle. 


Usrs. Anhydreus calcium chloride rapidly attracts moisture and 
deliquesces. It is therefore used to remove aqueous vapor from 
air or other gases. It is placed into cases of balances and desic- 
cators so as to permit cooling, preservation and weighing of filters, 
precipitates, etc., dried by heat, without absorbing moisture again. 
In suitable tube apparatus it is used to absorb the water produced 
by the oxidation of hydrogen or otherwise liberated, and thus to 
determine its weight. 

In solution Ca Cle is used as a general reagent for separating 
organic acids into groups. One group (oxalic, tartaric, racemic, 
citric, malic, etc.) is precipitated, their neutral calcium salts being 
either insoluble or difficultly soluble in water, while those of other 
groups (suecinic, benzoic, salicylic, ete., or acetic, formic, butyric, 
lactic, ete.) form soluble calcium salts. 

Addition of a few drops of Ca Cle solution tourine, in which glu- 
cose is determined by Fehling’s solution, if made just before the 
finishing point, serves to promptly settle the cuprous oxide by en- 
tangling the suspended particles in the gelatinous caleium tartrate 
and thus facilitates the perception of the end of the reaction. 
(Munk.) 

Tests. For many purposes of drying the anhydrous Ca Cle need 
not be pure. But for accurate gas analysis or for elementary 
organic analysis pure Ca Cleis required. It should be white, dry 
and either in solid, fused fragments, or in pieces of spongy texture, 
offering a larger surface for absorption. When too highly heated 
during the process of fusion, the last portions of the hydrate will 
decompose into Ca O and H Cl, leaving a product of alkaline reac- 
tion, capable of absorbing some C Oz. 

The crystallized salt, Ca Cle + 6 He O, is used for making the so- 
lution, and must be strictly neutral. Its dilute solution must yield 
no precipitate with Hz S, nor with ammonium sulphide or hydrate, 
nor with calcium sulphate or barium chloride. After precipitation 
with a mixture of ammonium carbonate, hydrate and chloride, the 
filtrate must not be precipitated by sodium phosphate (absence of 
magnesium). No ammonia must be evolved on heating with cal- 
eium or potassium hydrate. 

PREPARATION. Fragments of pure, white marble are added to dilute 
H Cl (1:6) until no more is dissolved. Some lime water is added to 
the solution, and then Hz S passed through it until a small filtered 
portion is no longer changed by ammonium sulphide. It is then 
poured into a flask, well corked and left for 24 hours in a warm 


f 


64 CALCIUM FLUORIDE—HYDRATE. 


place to deposit sediment. The clear filtrate is then accurately 
neutralized with H Cl, evaporated and left to crystallize. 

The crystals are dried on filter paper and either preserved to use 
for solution or made anhydrous by heating them untilthe opaque, 
dry mass, which at first results, fuses at the lowest possible tem- 
perature. The solution is prepared by dissolving 1 part of Ca Cle + 
6 He O in 5 parts of water. 


CALCIUM FLUORIDE, Ca Fz, 
fluorspar. 


Uses. To prepare hydrofluoric and hydrofluosilicic acid. 
Also, with potassium or sodium acid sulphate in blowpipe analysis, 
to liberate alkalies (especially lithium) from their silicates and 
recognize them by their flame color. Pure ammonium fluoride or 
liquid hydrofluoric acid or powdered cryolite are often used in 
preference. It is best to select pure crystals of the mineral and 
powder them, rather than buy an often impure commercial pow- 
dered fluorspar. 


CALCIUM HYDRATE Ca(0O H):. 


Usrs. Calcium hydrate (slaked lime) is used in the form of pow- 
der, in solution (as imewater), and in the intermediate state of a 
thin magma (as milk of lime). Lime water serves to detect carbou 
dioxide by the formation of insoluble calcium carbonate ; also to 
recognize tartaric and citric aeids, etc. In the form of milk or dry 
powder it is used to liberate ammonia from its compounds and to 
separate magnesia from the alkalies by converting magnesium 
salts in the insoluble hydrate, requiring 55,000 parts of water for 
solution. It is also used in the separation of alkaloids from the 
crude drugs; in the making of calcium hypochlorite and other 
preparations, among them the soda-lime, employed in ultimate 
organic analysis for determining the nitrogen in the form of am- 
monia. 

Tests. For some purposes the ordinary burnt lime furnishes 
preparations of sufficient purity, but for others a strictly pure 
article, free from alkalies, barium, strontium or magnesium, must be 
used. Alkalies are most easily detected by the spectroscope, the 
hydrate being for this purpose converted into chloride by adding H 
Cl. Limewater is quickly changed by the C Oz of the atmosphere, 
and must, therefore, from time to time, be tested for strength, by 
giving a strong alkaline reaction with test papers, and precipitate 
with sodium carbonate; or else kept saturated by keeping it in 
contact with excess of solid hydrate. At15°C., one part of calcium 
hydrate requires 780 parts of water for solution. It should give no 


CALCIUM HYPOCHLORITE. 65 


precipitate with solutions of calcium sulphate, potassium chromate 
or barium chloride. After precipitation with a mixture of ammo- 
nium carbonate, chloride and hydrate, the filtrate on evaporation 
should leave no permanent residue. 

PREPARATION. When only absence of alkalies is required, the 
ordinary hydrate may befreed from them by repeated boiling ina 
silver dish with distilled water, before making the solution or 
milk, or drying again for use in powdered form. Absolutely pure 
hydrate is made from pure calcium chloride by precipitating its so- 
lution with excess of ammonium carbonate, washing and drying 
the precipitate and then calcining it in a platinum crucible by pro- 
tracted application of a bright red heat until a small specimen no 
longer shows effervescence with dilute nitric acid. 

It is slaked by addition of one-half its weight of pure water and, 
after cooling, the product is preserved in close vessels. 


CALCIUM HYPOCHLORITE, Ca Cl: . Ca (0 Cl)2. 


Chlorinated Lime. Bleaching Powder. 


UsrEs. For a number of purposes for which chlorine is employed. 
For making solutions of alkaline hypochlorites ; converting alco- 
hol, acetone, etc., into chloroform. For recognizing aniline by 
the violet-blue color produced with hypochlorite alone, turned into 
rose-red by addition of ammonium sulphide; for liberating nitro- 
gen from urea; for distinguishing the spots of antimony from those 
of arsenic produced in Marsh’s test, As being soluble, Sb insoluble. 
For the convenient evolution of chlorine gas, bleaching powder 
is made into small cubes with plaster of paris, which are acted on 
by H Cl in an apparatus similar to that for evolving Hs S. 

Tests. A good commercial article is of sufficient purity, pro- 
vided it is free from arsenic. Its strength in available chlorine 
should not be less than 25%, the highest possible limit being 52.17. 
This is ascertained by titration with deci-normal sodium arsenite 
solution, of which 1 Ce. = 0.003537 Cl. 

Of the hypochlorite, 7.074 grammes are thoroughly mixed by 
trituration with water sufficient to fill a1 litre flask. After subsi- 
dence, 50 Ce. of the clear liquid (corresponding to 0.3587 gr. of 
hypochlorite) are transferred to a flask and deci-normal solution of 
sodium arsenite added from a burette until a drop taken out fails 
to give a blue color on starch paper prepared with zinc iodide. 
Each Ce. of arsenite used indicates one per cent of available chlo- 
rine. 

PREPARATION. On the large scale chlorinated lime is manufac- 
tured by passing chlorine gas into chambers containing, on shallow 


66 CALCIUM SULPHATE—CARAMEL—CARBON DISULPHIDE. 


shelves, freshly slaked lime, keeping the temperature below 26° C., 
80 as to prevent the formation of chlorate. 


CALCIUM SULPHATE, CaS 0; + 2H20. 
Gypsum, Plaster of Paris. 


Usrs. In saturated aqueous solution calcium sulphate is used to 
detect barium, strontium and oxalic acid. Moulded into small 
cylinders it is introduced into tubes to furnish water, as it re- 
linquishes its water of crystallization by heating. The partially 
dehydrated plaster of paris is used as a cement, etc. Also in blow- 
pipe analysis and assaying to fuse with fluorspar, etc. Molec. W. = 
171.784. 

Tests. Pure natural crystals of transparent gypsum (selenite) 
are selected. They require for solution at 15° C. 380 parts of water. 

PREPARATION. Into the bottles filled with pure water small frag- 
ments of crystals are introduced, so as to remain in excess and in- 
sure full saturation. 


CARAMEL. 


Usrs. A solution of caramel containing 100 grammes in 1 litre is 
used in sugar refineries as a standard of comparison for ascertain- 
ing the decolorizing power of boneblack. 

PREPARATION. Sugar is carefully heated to between 180° C. and 
200° C., and thus converted into dark-brown caramel. Of this 100 
gr. are dissolved in 200 Ce. of water, and 100 Ce. of alcohol added, 
then diluted to 1litre. After standing for some days, to allow de- 
positing the sediment, the liquid is filtered and preserved. 


CARBON DISULPHIDE, C Sz. 


Usss. As a general solvent of oils, fats, resins, gutta percha, caout- 
chouc, etc.; also of phosphorus, sulphur, iodine, arsenic chloride, 
bromide or iodide, etc. As a special reagent for the recognition of 
iodine, which dissolves in it with a beautiful violet color ; for alco- 
hol by the formation of cuprous ethyl-xanthate. For the prepara- 
tion of potassium sulphocarbonate, Ke C Ss, used for the detection 
of nickel, etc. 

It is also used to identify codliver oil. One drop of the oil added 
to 20 drops of carbon disulphide and 1 drop of conc. sulphuric acid 
produce a beautiful violet color, which soon fades. 

Trsts. Pure carbon disulphide is a mobile, colorless, very vola- 
tile and highly refractive liquid of peculiar odor, rather agreeable 


CERIUM DIOXIDE. 67 


when pure, but very fetid when impure, especially when contain- 
ing selenium or organic sulphides or mercaptans. At 15° C. its 
sp. gr. is 1.268; it boils at 46° C., but volatilizes at a much lower tem- 
perature. In water it is almost insoluble, but mixes in all propor- 
tions with alcohol and ether. 

The substances most frequently found as impurities are sulphur, 
sulphur dioxide, hydrogen sulphide and sometimes selenium and 
other impurities. Moist test papers should show neutral reaction 
(abs. of S Oz) ; lead carbonate or lead acetate solution should not be 
colored black or brown (abs. of Hz 8); on spontaneous evaporation, 
on a watch glass, no residue should remain (abs. of more than traces 
of water, sulphur, arsenic compounds, etc.) The odor should not’ 
be fetid nor the color yellow. 

PREPARATION. The use of absolutely pure carbon disulphide by 
perfumers for extracting the odors of flowers has caused it to be 
manufactured largely at very low prices, so that few will incur the 
risk of preparing or rectifying C Seon asmall scale. It is made by 
heating in a suitable distilling apparatus of stoneware or iron 
(Schroetter’s) pieces of pure charcoal to a bright red heat, and then 
introducing, through a side tube, pieces of pure sulphur. The vapor 
is condensed and rectified by redistillation at a temperature not 
exceeding 50° C.; the distillate is shaken with solution of potassium 
permanganate, decanted and, if necessary, redistilled at a low tem- 
perature. 


CERIUM DIOXIDE, Ce O2, and CERIC HYDRATE, Cez2 0(0 H)s. 


Usrs. This has been reeommended by Sonnenschein, under the 
older name of ceroso-ceric oxide, as one of the most delicate re- 
agents for strychnine. When a small amount is brought together 
with strychnine and concentrated sulphuric acid the same series of 
colors are produced as with other oxidizers, potassium dichromate, 
permanganate, lead dioxide, manganese dioxide, etc. A deep blue 
at first, passes through violet into red. The cerium produces the 
reaction with smaller amounts of strychnine and the successive 
colors change much more slowly, so as to give better opportunity 
for observation. The hydrate being more soluble is preferable to 
the anhydrous dioxide. 

Tests. Cerium salts are rarely found in commerce entirely free 
from didymium and lanthanum, but these do not interfere unless 
in too great a quantity, soitis best to test the specimen to be used 
by producing the colors with a minute crystal of strychnine and 
sulphuric acid, 


68 CHARCOAL—CHINOIDINE IODOSULPHATHR. 


PREPARATION. The anhydrous oxide is obtained by heating to 
redness either the oxalate or the nitrate of cerium. The hydrate is 
formed by precipitating cerous hydrate from a solution of the ni- 
trate or oxalate by the addition of potassium hydrate. Thisis kept 
stirred up in the solution while either chlorine gas is passed through 
(or solution of calcium hypochlorite is added), until the precipitate 
has been converted into the brownish-yellow ceric hydrate, Ce2 O 
(O H)s. This is separated by filtration, washed, dried and care- 
fully preserved. 


CHARCOAL. 


UseEs. In solid pieces, wood charcoal serves as a support in blow- 
pipe operations ; also for purifying alcohol from fusel oil previous 
to rectification by distilling. In powder, different varieties of car- 
bonaceous material, wood, charcoal, coke, lampblack, ete., are used 
for the reduction of oxides, ete., at hightemperature. (Preparation 
of potassium iodide, bromide, barium sulphide, ete.) Animal char- 
coal, principally boneblack, is used for the removal of coloring ma- 
terials in the purification of alkaloids, sugar, urine, etc. 

For blow-pipe supports, a thoroughly burned charcoal, derived 
from pine or other soft wood, is preferable. It should he selected 
of straight, parallel fibre, free from knots or bark, and split into 
pieces of five to six inches in length, two inches broad and about 
three-quarters to one inch thick, the surface used presenting a 
radial section. Finely powdered charcoal, compressed into pieces 
of suitable shape and size, are now sold for the same purpose. 


CHINOIDINE IODOSULPHATE. 


Us es. This reagent has been introduced by De Vrij for the esti- 
mation of quinine in a mixture of cinchona alkaloids, by precipita- 
tion as herapathite. Its use is based on the difference in solubility 
of the iodosulphates (herapathites) of the cinchona alkaloids. The 
assay is made as follows: In a beaker, very gently heated on a 
water-bath, 1 gramme of the alkaloids is dissolved in a mixture of 
19.69 grammes alcohol of 94% and 0.31 gr. sulphuric acid, and, after 
solution, 30 grammes alcohol are added. The solution of the re- 
agent is then added, drop by drop, with constant stirring, until the 
color of the solution has become an intense yellow. This is due to 
the yellow cinchonidine iodosulphate remaining in solution, while 
the darker quinine salt precipitates, showing red stripes whenever 
the beaker is rubbed by the stirring rod. The heat is now increased 
sufficiently to redissolve the precipitated quinine salt, and the 
beaker is set aside for twelve hours to deposit the crystals, which 
are weighed. One part of herapathite corresponds to 0.55055 of 
quinine. z 


CHLORAL HYDRATE. 69 


PREPARATION. On a water bath dissolve 2 parts of chinoidine in 
4 parts of benzol; after cooling, decant the clear liquid and agi- 
tate it thoroughly with 2 parts of dilute sulphuric acid (1 : 10). 
Transfer to a porcelain capsule, and add to it asolution of-one part 
iodine and two parts potassium iodide in 50 parts of water, drop 
by drop, and with constant stirring. Chinoidine iodosulphate pre- 
cipitates. After washing it by repeated addition of water and de- 
canting, one part is dissolved in six parts of alcohol, by careful 
heating on a water bath. The solution is set aside to cool and de- 
posit its less soluble portion. The clear liquid is separated, evapo- 
rated almost to dryness, and one part of the residue is dissolved in 
five parts of cold alcohol and carefully preserved. 


CHLORAL HYDRATE, C2Cls H O+ H:20, 


Uses. When chloral hydrate is brought together with an alka- 
line sulphide, especially ammonium sulphide, a deep red-brown 
precipitate is formed, of such intensity of color that the reaction 
may be used, not only for the recognition of chloral, but also for’ 
ammonia, and for HeS. Chloral hydrate dissolved in freshly satu- 
rated sulphuretted hydrogen water’ produces, with even small 
traces of ammonia, a distinct yellow to red-brown ; when dissolved 
in ammonia water it serves, by the same reaction, to detect small 
amounts of hydrogen suiphide. : 


Chloral hydrate also serves to detect naphthol. The substance 
containing the naphthol is dissolved in concentrated solution of 
potassium hydrate. On addition of a small crystal of chloral hy- 
drate (or a drop of chloroform), and heating, it turns deep blue, if 
even traces of naphthol are present (Lustgarten). 


Chloral hydrate, as well as the alcoholate and metachloral, have 
also been proposed as aids in differentiating essential oils, for 
recognition of digitalin, etc. 

A solution of 12% of chloral hydrate is used in microscopical 
investigations to render transparent some vegetable tissues, e. g., 
the epidermis of wheat or rye grains, etc. It is also used to dis- 
solve alkaloids, and for this purpose a solution in 4 parts of 
glycerin is sometimes employed instead of the above, in water. 
Also for preparing trichloracetic acid. 


Tests. For all the above purposes crystals of chloral hydrate, 
as now sold, are sufficiently pure. 


PREPARATION. By passing dry chlorine gas slowly, but without 
intermission for several weeks, into alcohol of no less strength than 


5 


107 a CHLORINE. 


0.8086 spec. grav. (97% by volume, or 95.34% by weight). When no 
more hydrochloric acid gas is formed, even by raising the tempera- 
ture to 65° C., the product is heated with an equal volume of cone. 
sulphuric acid, distilled, purified by redistillation and then con. 
verted into hydrate by addition of the necessary amount of water. 
Chloral, Ce Cls H O, = 146.018; chloral hydrate, C2Cls HO + HzO 
= 163.978. 


CHLORINE Cl and CHLORINE WATER. 


Usses. To convert metals and their oxides into chlorides, thereby 
rendering them soluble, e. g., gold, platinum, etc.; to decompose 
sulphides ; to liberate bromine and iodine from their compounds. 
To oxidize in the presence of water a number of bodies, by uniting 
with the hydrogen to form hydrochloric acid, while oxygen is lib- 
erated. It is hence employed in the oxidation of nickel, in the 
preparation of ceric hydrate, ferricyanides; in the quantitative 
determination of bromine and iodine in their silver salts, ete. In 
organic bodies it is capable of substituting H, e. g., in the preparation 
of chloral, in bleaching indigo, etc. It also serves as a special rea- 
gent for quinine and quinidine (thalleioquine reaction). It is used 
either as gas, well dried, or in saturated watery solution as chlor- 
ine water. 

Tests. Chlorine water must be well saturated, and, as it rapidly 
deteriorates, even by the most careful keeping, should be frequently 
renewed. It may be examined with volumetric arsenic solution, as 
described under calcium hypochlorite, gq. v. It should not contain 
hydrochloric acid (asit will when long or carelessly kept). Thismay 
beascertained by shaking with some metallic mercury until the odor 
has entirely disappeared, when the acid reaction of the liquid will 
indicate the presence of H Cl. When shaken with chloroform or 
carbon disulphide, these reagents must not become colored, even 
transiently ; a brownish color would indicate bromine ; a violet, 
iodine. 

Dry chlorine gas has a greenish-yellow color; specific grav. 35.37 
(H =1). Itisvery corrosive, irrespirable, and shows great affinity 
for hydrogen. It is tested by dissolving in water and examining 
as above. 

PREPARATION. Chlorine may be prepared in a variety of ways; 
by bringing together hydrochloric acid with potassium perman- 
ganate or dichromate, or manganese or lead dioxide, etc. The 
best method is that of Wiggers: A eapacious flask is fitted with a 
safety-funnel tube and a delivery tube. The latter communicates 
with a small wash bottle containing water (or in case dry gas is to 
be used, concentrated sulphuric acid). From this, a tube leads 


CHLOROFORM 71 


to a U tube containing fragments of Mn Oz, to remove H Cl, and 
then connects with the apparatus for decomposition, or with the 
flask containing water to be saturated. Into the evolution flask 
is placed an intimate mixture of 15 parts of high grade mangan- 
ese dioxide (free from lower oxides of manganese and from lime- 
stone), with 18 parts of dry sodium chloride. To this a cooled mix- 
ture of 45 parts of conc. sulphuric acid (free from arsenic) and 21 
parts of water is added, and the mixture thoroughly shaken together. 
The flask is now closely attached to the apparatus and, after re- 
jecting the first portion, contaminated with the air in the apparatus 
(and containing bromine, if any was present in the salt), the chlor- 
ine is used to saturate the water or for other purposes. 

After saturation, the chlorine water must be preserved in well- 
closed bottles, in a cool place, with perfect exclusion of light. 
Ample precautions must be taken to avoid inhalation of the gas. 

Recently, Winkler has proposed to prepare chlorine from hydro- 
chlorie acid and calcium hypochlorite, the latter being made up 
into cubes of suitable size by,admixture with plaster of paris. A 
Kipp’s apparatus is employed, and renders the regulation of the 
supply of chlorine easy. 


CHLOROFORM, C H Cls, 


UsEs. Chloroform is employed as a solvent for iodine, bromine, 
phosphorus, sulphur, etc.; for gutta percha, caoutchouc, Canada 
balsam, resins, oils, fats,"paraffin, many alkaloids, etc. Hence, it 
is useful for removing these substances from mixtures, for recog- 
nizing iodine by the violet color of the solution ; for differentiating 
alkaloids according to Dragendorf’s process by successive applica- 
tion of various solvents (benzin, benzol, chloroform, amyl alcohol, 
etc.). Also, for the assay of cinchona barks a mixture is used by 
Prollius consisting of 20 parts of chloroform, 76 parts alcohol and 4 
parts of ammonia water, the chloroform being substituted in 
special cases instead of the ether usually employed. It also forms 
a very delicate reagent for the detection of naphthol by the pro- 
duction of a blue color by boiling it for some minutes with its alka- 
line solution (Lustgarten). To detect even minute quantities of ani- 
line (Hoffmann) and aniline dyes, rosaniline derivatives, etc. (Curt- 
man), by the production of malodorous isonitrils, when heated with 
them and alcoholic solution of alkaline hydrates. In wine analysis 
it serves to detect adulterations with various coloring materials 
(cochineal, elderberries, red currants, logwood, rose or poppy pe- 
tals, etc.)(De Groot). Mol. W. = 119.084. ; 

Tests. Pure chloroform is a colorless, volatile liquid of a burn- 
ing, sweetish taste and a peculiar ethereal odor. Spec. gray. at 15° 


5* 


72 CHROMIUM COMPOUNDS—CHROMOUS CHLORIDE. 


C., 1.499. It is readily decomposed by light and air; hence, it should 
be preserved as much as possible excluded from both. Addition of 
a small amount of pure alcohol protects it from change and is not 
objectionable for analytical purposes. Choroform boils at 60° 
—61°C. Itis soluble at 15° C. in 200 parts of water, and mixes with 
alcohol in all proportions. When purified with impure oil of vit- 
riol it is liable to contain arsenic, and must, therefore, be tested for 
its absence. Its solution in water must be neutral to test papers ; 
it must give no precipitate with silver nitrate (abs. of free chlorine 
and arsenic). At ordinary temperatures it must completely vola- 
tilize without residue. In contact with pure conc. He S O4 no 
browncolor must appear. It must not liberate iodine from a solu- 
tion of pure potassium iodide; hence, no violet color must be pro- 
duced by mixing them. 

PREPARATION. On the large scale, chloroform is made by distill- 
ing 820 parts of bleaching powder (35% of active chlorine) with 100 
parts of strong alcohol, U. S. P. The distillate is rectified after 
agitation with conc. sulphuric acid. By using acetone instead of 
alcohol a purer product is obtained in greater abundance. 

On asmall scale, pure chloroform may be prepared by distilling 
3 parts of chloral hydrate with a solution of 1 part of potassium hy- 
drate in 10 parts of water, and purifying the product by redistilla- 
tion from a water bath. 


CHROMIUM COMPOUNDS. 


Chromic Acid, see page 6. 


CHROMIC ALUM, Cre K2(S O4)4 + 24 HeQ, and CHROMIC SUL- 
PHATE, C2 (S O4)s3 + 18 He O. 


Usss. A few drops of the watery solution of either of these salts 
are added, together with some ammonium chloride, to volumetric 
solution of gelatine for titration of tannic acid for the purpose of 
facilitating the separation of the flocculent precipitate, and thus 
determining the final point (Johanson). 

The commercial articles are of sufficient purity. 


CHROMOUS CHLORIDE, Cr Cle. 


UsED as an absorbent of oxygen in gas analysis (Von-der Pford- 
ten.) 

PREPARATION. Two parts of chromic acid are heated with 15 
parts of hydrochloric acid of spec. gr. 1.16, and the resulting green 
solution of chromic chloride is reduced to blue chromous chloride © 


CINCHONAMINE—COBALT COMPOUNDS. 3 


by immersion of metallic zinc. This is done within the gas absorp- 
tion apparatus, so as to use the solution before coming in contact 
with air. By absorption of oxygen the blue solution turns green. 


CINCHONAMINE, Cio Hos Ne O2. 


Uses. This alkaloid occurs in a dark brown variety of cinchona 
bark from Colombia; its nitrate, Cig Ha Ne O2. HN Os, is almost 
insoluble in water, acidulated with nitric or acetic acid, and upon 
this insolubility the method of Arnaud and Pade for determining 
nitric acid in nitrates by precipitation is founded. The alkaloid is 
by careful neutralization with sulphuric acid converted into sul- 
_ phate (Cig Hos Na O2)2 . H2 S Os, which is easily soluble in water, and 
with this solution the soluble nitrates are precipitated. The 
molecular weight of Ci9 Hos Ne Oz is 311.39. 

Tests. The alkaloid crystallizes is colorless, anhydrous prisms ; 
melts at 195° C. and turns polarized light to the right [(¥ )p = + 
117.9]. It is insoluble in water ; at 17° C. it dissolves in 100 parts of 
ether and in 31.6 parts of 90% alcohol. The taste is only feebly 
bitter ; the solution of the sulphate does not fluoresce. 


Citraconic Acid, Cs He O.. 


This acid, obtained by distilling dry citric acid, is occasionally 
used for the separation of primary from secondary and tertiary 
amines. The primary amines form with it amides (resp. anilides), 
which, on account of less volatility, are, on distillation, retained 
as residues, while the secondary and tertiary distil over (Michael). 


COBALT COMPOUNDS. 


COBALTOUS NITRATE, Co (N Os)2-+ 6 Hz 0. 


Usrs. Cobaltous nitrate is used in blowpipe analvsis, especially 
for the detection of aluminium salts, which give with it an opaque, 
blue mass (Thenard’s blue), and of zinc salts which, on heating 
with it, give a yellowish green (Rinmann’s green), These reac- 
tions, however, furnish no absolute proof of the presence of alum- 
inium and zinc, for cobaltous nitrate produces a transparent blue 
glass with alkaline phosphates, borates and silicates and an opaque 
blue, not only with aluminium, but also with earthy phosphates 
and silicates; and a green of various shades with tin, titanium, 
antimony and niobium compounds. Those of magnesia and tan- 
talic acid produce a flesh-colored mass; barium, a brown-red ; 
beryllium, calcium and strontium, a gray mass. 


seat 


hn 


14 COBALT COMPOUNDS. 


Tests. The impurities most likely to occur in cobalt compounds 
arise from the metals ordinarily associated with it in the ores: 
nickel, iron, manganese, copper, silver, bismuth, arsenic, lime, 
magnesia, etc. Its solution, acidulated with H Cl, should give no 
precipitate with hydrogen sulphide. After precipitating the aque- 
ous solution with ammonium sulphide, the filtrate should, on heat- 
ing upon platinum foil, leave no fixed residue. When to the solu- 
tion potassium cyanide is added until the precipitate is redissolved, 
and then bromine or sodium hypobromite added, no black precipi- 
tate of nickelic hydrate should fall, even after an hour’stime. The 
cobaltous nitrate of commerce is generally of sufficient purity. 
Co (N Os)2 + 6 He O = 270,449. 

PREPARATION. The pure metal is dissolved in dilute nitric acid, 
the solution concentrated and crystallized. A 10% solution in 
water is usually employed. 

Pure metallic cobalt may be obtained by the following process: | 
Any rich cobalt ore, either the speiss cobalt (smaltine), Co Ase, or 
cobalt glance (cobaltine), Co Ase. Co Se, or earthy cobalt, is finely 
powdered and roasted until all volatile ingredients are driven off. 
Ten parts are then mixed with one part of ferrous sulphate, and 
the mixture is introduced, in small portions, into a hessian erucible 
containing 30 parts of potassium disulphate fully melted. 

The heat is continued until the mixture is thoroughly fused and all 
evolution of sulphuric acid vapor has ceased. It is then extracted 
by boiling water, which extracts cobaltous sulphate, leaving be- 
hind the arsenic as ferric arsenate, and most of the iron and nickel, 
calcium sulphate, etc. The filtered solution is slightly acidulated 
and saturated with hydrogen sulphide, so as to precipitate the 
metals of the fifth and sixth analytical groups. It is again filtered, 
hydrogen sulphide expelled by boiling, and a concentrated solution 
of potassium nitrite, and then acetic acid is added. After com- 
plete precipitation, the yellow potassium-cobaltic nitrite, Coe (N 
O2)s . 6 K N Osc (Fischer’s salt) is separated by filtration and thor- 
oughly washed with cold water. It is then dissolved in boiling hy- 
drochloric acid ; the solution, containing cobaltous chloride and 
potassium chloride, is concentrated by evaporation and mixed with 
about an equal volume of ammonia water and ten percent solution 
of ammonium chloride, and set aside for several days, covered so 
as to admit free access of air. When the color has become a pure 
red purple, and when a small sample no longer turns blue on add- 
ing an excess of hydrochloric acid, it is supersaturated with hydro- 
chloric acid, and the temperature raised to boiling heat. Nearly 
the entire amount of cobalt separates in crimson-colored, quadratic 


‘erystals of purpureo-cobalt chloride, Co2(N Hs) Cle. This is heated. 


LUTEO-COBALTIC CHLORIDE—SODIO COBALTIC NITRITE. 75 


to redness in a current of hydrogen, when pure metallic cobalt re- 
mains as a gray powder. 


LUTEO-COBALTIC CHLORIDE, Coz (N Hs)i2 Cle. 


Usss. This reagent produces at once in a solution of alkaline 
pyrophosphates a crystalline orange-colored precipitate, which 
does not form with ortho or metaphosphates until the lapse of con- 
siderable time. Hence, it serves to distinguish and separate pyro- 
phosphoric acid (Braun), 

PREPARATION. Cobaltous chloride is first made by dissolving 6 
gr. of metallic cobalt in 22 Cc. of conc. hydrochloric acid and ob- 
taining crystals by concentration. A mixture of 1 part of cobal- 
tous chloride, 1 part ammonium chloride, 1 part potassium per- 
manganate and 6 parts of concentrated ammonia water is then 
heated in a closed vessel for 24 hours to 70° C. The orange-eolored 
liquid is separated by filtration, and any erystals remaining in the 
residue are redissolved out by boiling water containing 5 per cent 
of hydrochloric acid. The solution is evaporated somewhat, and 
then an excess of very cone. hydrochloric acid is added. This pre- 
cipitates the luteo-cobaltic chloride in brownish-yellow crystals, 
which may be purified by recrystallization from boiling water. 
The test solution is made by dissolving one part of the reagent in 
20 parts of water. 


SODIO-COBALTIC NITRITE, Coz (N O2)¢. 6 NaN Oo. 


Users. For the detection of potassium, with which it forms a 
yellow precipitate, Co2(N O2)6.6 K N O2 + X& He O ( Fischer’s salt), 
which is hardly soluble in cold, somewhat more in hot water, in- 
soluble in alkaline chlorides, nitrites, acetates or in dilute acetic 
acid. It dissolves in boiling hydrochloric acid. Cesium, rubidium 
and ammonium salts form similar precipitates. Potassium salts 
are precipitated from very dilute solutions, where platinic chloride 
no longer shows a reaction. As no precipitate is formed with the 
salts of the alkaline earths, zinc, magnesium or iron, they need not 
be removed from solution before application of the reagent for the 
precipitation of potassium (Curtman). 

PREPARATION. A solution of 4 grammes cobaltous nitrate is 
mixed with one of 10 gr. sodium nitrite, both in very little water, 
and 2Cc. acetic acid are added and then water to fill up to 100 Ce. 
(Curtman). Cobaltous chloride may be used instead of nitrate (LD. 
L. de Koninck). 

Cebalt paper is occasionally used as an indicator for “‘spotting,”’ 
jn the volumetric determination of zinc, copper, etc., by sodium 
sulphide. It is made by dipping strips of filter paper into an alco- 


16 CULOR REAGENTS. 


holic solution of cobaltous chloride, colored bya little aniline blue, 
so that only one-half of the length of the strip becomes stained, while 
the other half remains white. A drop of the mixture to be tested for 
excess of sulphide is placed on the white end, so that by spreading 
over the paper the liquid may reach the stained end and color it 
black in case of an excess of the sulphide. 


Cochineal; see Color Reagents and Indicators, page 77. 


COLOR REAGENTS AND INDICATORS. 


Under this designation a number of various coloring agents are 
described, which have the property of forming with acids and with 
alkalies compounds different in color, so that in neutralizing acids 
or alkalies, and especially in volumetric analysis, they indicate the 
point of neutralization. Others serve as colorimetric reagents by 
observation of the various degrees of intensity of color, produced by 
different amounts of the colored compounds, produced by them 
with certain chemicals. Some of them are derived directly from 
plants or animals, others are artificial products prepared from ani- 
line, phenol, anthracene, naphthalin and other aromatic com- 
pounds produced by the coaltar industry. Nearly all of them are 
used only in small quantity and the state in which they are found 
in commerce, as manufactured on the large scale for the purposes 
of the dyer and calico printer ; hence, in most cases, there is no 
occasion to describe tests for their purity, nor processes for prepar- 
ing them on the small scale. Many of the indicators will serve 
equally well for all general purposes, but there are distinct features 
in the behavior of several of them, which make them valuable for 
differentiation. Thus, litmus and phenol-phthalein indicate alka- 
line reaction with hydrates and carbonates, but not with dicarbon- 
ates, while methyl-orange, lacmoid, Poirier’s blue, etc., show the 
alkaline reaction with diearbonates as well. Phenol-phthalein does 
not show the alkaline reaction with aniline, toluidine or quinoline, 
but reacts with the acids of their salts as if no base was present; 
litmus remains unaffected by them, while methyl-orange shows the 
alkaline reaction of the free bases. Urine, which shows acid reac- 
tion with litmus and phenol-phthalein, gives an alkaline reaction 
with lacmoid on account of the bases of the phosphates, ete., etc. 

Thus, by a judicious use of different indicators, valuable informa- 
tion may be obtained. 


COLOR REAGENTS. 77 


Aurin; see Rosolic Acid, page 19. 


BENZOPURPURIN B., Cs: Has Ng Os S2 Naz. This is one of the 
tetrazo-tolidine colors, allied to congo-red. Its aqueous solution is 
orange-red, turning violet on addition of acids ; red with alkalies. 
While useful for general purposes it is especially so in the titration 
of pyridine, which does not give an alkaline reaction with litmus 
or tropzolin, while ethyl-orange and benzopurpurin B. show with 
it alkaline reaction. Paper saturated with its solution, rendered 
violet by a minimum of acid, forms a very delicate reagent for 
traces of gaseous ammonia. | 


Brazilwood, see on page 58. 


CABBAGE, RED. The leaves to water or dilute alcohol yield a 
violet color ; turned red by acids ; green by alkalies. It is suitable 
to all purposes of alkalimetry, including ammonia. Paper stainea 
with it makes a very sensitive test paper. 


Cobalt paper ; see Cobalt Compounds, page 5. 


COCHINEAL. The insect contains a coloring material, soluble 
in water and alcohol, whose principal constituent is carminic acid, 
Ci Hig Ow. The tincture is made by macerating 1 part of the whole 
cochineal with 80 parts of 20 to 25 percent alcohol. It reddens lit- 
mus paper. The color is a yellowish-red, turned violet by alkalies, 
restored by acids and shows well by artificial light. Salts of iron, 
alumina, lead, copper and alkaline acetates interfere. ‘The tinc- 
ture is very sensitive to alkalies and alkaline earths, even their 
carbonates and dicarbonates producing the violet color ; hence, it 
is for these preferable to litmus, and stands equal to lacmoid ; for 
ammonia it is superior to phenol-phthalein; for organic acids, 
it is less sensitive and inferior to litmus. By soluble lead salts, 
even in very dilute solution, it is colored a peculiar purple-violet 
and is, therefore, used to detect lead in drinking water. It is 
also employed for staining vegetable tissues in microscopic investi- 
gations. : 


COLEUS VERSCHAFFELTI. The strong alcoholic tincture of 
the deep red leaves of this common garden plant has been recom- 
mended by Boetiger; it turns green with alkalies, red with acids. 
It contains the purple, resinous Colein, Cio Hio Os. 


CONGO RED, -Csz Hee Ne O¢ Se Naz, a naphthyl-amine-tetrazo- 
benzidine color, made by the action of tetrazo-diphenyl] chloride on 
naphthionic acid. It dissolves in water with a bright red color, 
changed to blue by acids and restored to red by alkalies. It indi- 
cates free mineral acids by a blue color, even if only a trace is 


78 COLOR REAGENTS AND INDICATORS. 


present (0.0019% of HCl), while neither acid salts, such as alum- 
inium sulphate, potassium dichromate, etc., nor acetic or other or- 
ganic acids produce any change. On the other hand, it is very sen- 
sitive to a number of alkaloids, to aniline, toluidine, etc., which re- 
store to red the color changed to blue by acids, so that it proves a 
useful indicator for their titration. It is extensively employed in 
the clinical analysis of gastric juice, in which it indicates the small- 
est traces of free hydrochloric acid. It is useful in testing acetie 
acid, which, when pure, does not change its red color, while the 
presence of a trace of sulphuric or hydrochloric acid turns it 
blue. ' It is generally used as congo paper, made by soaking unsized 
paper in a watery solution of 1%, and drying. The color is retained 
firmly, even if the paper is thrown into liquids. 


Corallin: a compound of aurin and methylaurin; see Rosolic 
Acid, page 19. 


CURCUMIN W. The commercial name for a stilbene color, 

soluble in water with greenish-yellow color, and turning red with 
the least trace of alkali. Like phenol-phthalein, it does not indicate 
dicarbonates. It is suitable for titration of ammonia. 


CYANIN or QUINOLINE-BLUE, Cz Hs; NoI, used for sensitiz- 
ing photographic dry plates; crystals of green metallic lustre, 
soluble in alcohol; is occasionally used as indicator. It turns blue 
with alkalies, colorless with acids. 


m DIAMIDO-BENZOL or m PHENYLENE-DIAMINE, Ce. Hz 
(N He)e (1 : 8), is obtained, in the form of a grayish crystalline 
powder, by the reduction of meta-dinitrobenzol. It is a strong 
base, little soluble in water, easily dissolved by alcohol or ether. 
It serves for the detection of nitrites, especially small quantities 
found in drinking water. The free nitrous acid (liberated from the 
nitrites by sulphuric acid) produces with it a yellow color, so in- 
tense that even traces of it become visible. Hence, phenylene- 
diamine may be used as a colorimetric indicator, and by compari- 
son of color with a standard of known strength an approximate 
quantitative determination may be made. For water analysis one 
part of meta-phenylene-diamine is dissolved in 200 parts of water. 
Of this solution, 1 Cc. is added to a mixture of 100 Ce. of the water 
under examination with 1 Ce. of dilute sulphuric acid (1 : 8). 


DIMETHYL-AMIDO-AZOBENZOL-SUPHONIC ACID, (C Hs), 
N.CeHs4.N:N .CeHs.S03H,is knownin commerce as Helianthin 
‘(see page 21), Methyl Orange, Poirier’s Orange, III, or Tropaeolin, D. 
This, as well asits base, is a usefulindicator; the base being by some 
preferred on account of a greater difference in the (+) yellow color of 


COLOR REAGENTS AND INDICATORS. 79 


alkalies and the (—) crimson red of acids. But they are nearly of 
equal value, and the sulphonic acid is more easily procured. The de- 
scription of their application will answer for both. 

The yellow solution is turned crimson red by even small traces: 
of free mineral acids and restored by alkalies. Neither hydrogen 
sulphide, arsenous nor carbonic acid interfere with this effect. 
It is suitable as indicator for hydrates, carbonates, dicarbonates, 
borates, silicates, arsenites and sulphides of the alkalies and alka- 
line earths ; also for all free mineral acids, especially for the titra- 
tion of phosphoric acid, in which the change from (—) red to (+) 
yellow occurs as soon as the primary salt, Na He P Ou, is formed. 
It will show alkaline color with aniline, toluidine, quinoline and 
many alkaloids, which do not show any reaction with phenol-phtha- 
lein. It cannot be used in hot liquids. About 5 drops of the solution 
are used for 100 Cc. of the liquid used for titration. The solution 
of methyl orange contains 1 part in 1,000 parts of water. That of 
the base 1 part in 200 parts of alcohol. 


DIPHENYL-AMINE, (Ce Hs)2 N H, is obtained by the dry distilla- 
tion of aniline blue (triphenyl-rosaniline) in grayish crystals, melt- 
ing at 54° C., slightly soluble in water, more solublein acids. A1% 
‘solution in conc. sulphuric acid (forming diphenyl-sulphonie acid) 
is colored intensely blue by nitric aeid ; also, temporarily by nitrous 
acid, |fading to greenish yellow; also, somewhat less intensely by 
hypochlorous, bromic and iodic acid ; tosome extent by chromic, 
vanadic, permanganic, molybdic and selenous acid, some ferric 
salts, barium and hydrogen dioxide. A red color is produced by 
-ehloric acid. Ozone colors the alcoholic solution of diphenylamine, 
or papers stained with it, yellow to brown. It is principally em- 
ployed to detect small quantities of nitric acid in sulphuric acid 
and nitrates in drinking water, also in wine or milk diluted with 
well water containing nitrates. The bluecolor is so intense, that 1 
part of nitric acid can be shown in 3,000,000 of water, if to 1 Cc. of 
water a few drops of the solution are added and then 1 Ce. of conc. 
sulphuric acid, so as to form a layer beneath the water. The zone — 
of contact is colored blue. The color disappears by addition of 
stannous salts. Hence, the quantity of nitric acid may be volumetri- 
cally determined, according to Longi, by using aj normal solu- 
tion of stannous potassium sulphate with diphenyl-amine as indi- 
cator. 


EOSIN, Ke Ca He Bra Os, or tetrabromfluorescein-potassium, is a 
phthalein color, forming red crystals, soluble in 2 parts of water 
with a deep yellowish-red color. In dilution the color is reddish- 
yellow by transmitted light, showing green fluorescence by re- 


80 COLOR REAGENTS AND INDICATORS. 


flected light. Addition of acids destroys the fluorescence and pre- 
cipitates the color, leaving a colorless liquid. Alkalies restore color 
and fluorescence. It has been especially recommended for titra- 
tion of soap (Fleischer). 

Ethyl Orange, one of the azo colors, in composition and uses 


very similar to methyl orange, see above dimethyl-amido-azo-benzol- 
sulphonic acid. 


EUPITTONIC ACID, Ci Hs (O C Hs)s Os (Hexa oxymethyl-aurin, 
Reichenbach’s Pittakal). Long orange needles, obtained during 
the manufacture of creasote by oxidation of beechtar oils. It is 
slightly soluble in water or alcohol. The*solution is colored blue 
by alkalies, brownish-yellow by acids. 


ferric alum,used as indicator for rhodanates, see iron com- 
pounds. 


FLAVESCIN, obtained by dry distillation of oakwood at low 
temperature ; soluble in ether, alcohol and water ; the yellow solu- 


tion is rendered colorless by acids, and yellow again by alkalies 
(Lux). 


FLUORESCEIN, C2 Hie Os, is the anhydride of resorcin-phtha- 
lein, made by heating to 195—200° C. a mixture of 7 parts of re- 
sorcin with 5 parts of anhydrous phthalic acid, and purifying by 
solution in sodium hydrate and precipitation by sulphuric acid. 
It dissolves in alcohol with orange-red color and green fluorescence, 
which disappears on addition of acids. It is especially suitable for 
the titration of dark colored gas waters, etc.,in which a color 
change can not be observed, while the disappearance of fluores- 
cence is sharply marked. It is kept in the very dry state. When 
needed, a few crystals are dissolved in alcohol, the solution diluted 
with water and added to the gas liquor until fluorescence appears 
plainly. 


FUCHSINE or ROSANILINE HYDROCHLORATE, C2 Hig Ns . 
H Cl (Triamido-diphenyl-tolyl-carbinol). The crystals have a 
green metallic lustre and transmit red light. They are slightly 
soluble in water, readily in alcohol with a crimson red color, in- 
soluble in oils. Addition of acids changes the color to yellow; 
great dilution with water or neutralization by alkalies restores the 
color; ammonia and caustic alkalies also discharge to color of the 
aqueous solution. Hence, Fuchsine has been tried as an indicator, 
but is unsatisfactory. It is used to detect alcohol as an adultera- 
tion of essential oils, being insoluble in the oils, but soluble in 
alcohol, its dissolving in and coloring the oil shows admixture of 
alcohol. Fuchsine, dissolved in glacial acetic acid, is used as a 


COLOR REAGENTS AND INDICATORS. 8} 


delicate reagent for nitrous acid (nitrites), whose presence changes 
the original crimson color, successively, to violet, then blue, green, 
yellow and finally toorange. Dilution with water does not restore 
the original color; nitric acid does not produce the color changes. 

Fuchsine-sulphurous acid is a delicate reagent for aldehydes and 
some of their derivatives (it reacts with chloral, but not with chloral 
hydrate). It is prepared by passing S O2 into a dilute solution of 
fuchsine in water until the color has changed to a pale yellow. 
The reagent may be preserved without change in well-closed 
bottles. The addition of a small quantity of an aldehyde produces 
an intense violet-red color. 

Fuchsine Paper. When paper is dipped into a solution of fuchsine, 
rendered yellow by sulphuric acid, and dried, it becomes a sensi- 
tive indicator of ammonia gas, which colors it red. 


GALLEIN, or Pyrogallol-Phthalein, C2 Hio Os, is obtained by 
heating for some hours an intimate mixture of 1 part of anhydrous 
phthalic acid with 2 parts of pyrogallol to 190° to 200°C. The 
fused mass is dissolved in strong alcohol and precipitated by water. 
Itis a brown crystalline powder, with green metallic lustre, almost 
insoluble in cold, and but slightly in hot water; alcohol dissolves 
it with dark red color. In alkaline hydrates it dissolves with red 
color as long as itis in excess ; with excess of alkali the color is deep 
blue, or in dilution, violet. Acids change the color to a pale yellow. 
It is a suitable indicator for ammonia, as well as for the fixed alka- 
line hydrates, carbonates and dicarbonates, for carbonic acid does 
not affect it. It indicates organic acids well and for their titra- 
tion is preferable to methyl-orange (Dechan). 


GENTIANA VIOLET, crystals of pale green metallic lustre, 
easily soluble in water with violeé color, whichis unchanged by 
alkalies, but indicates small traces of acids by turning blue (or 
green with greater excess). It is much used for staining of micro- 
organisms, urinary casts, etc. 


GEORGINA or DAHLIA. The petals of the dark violet varie- 
ties yield to alcohol and watera coloring matter (anthocyanin), 
which, like that of coleus or red cabbage leaves, is colored green 
by alkalies, red by acids. It is often used in the form of paper im- 
pregnated with the tincture. 


GUAIACUM, TINCTURE AND PAPER. The freshly prepared 
tincture and paper is turned blue by ozone, and, therefore, serves 
to detect ozone and various substances capable of setting it free. 
When added to urine containing pus, the blue color is produced. 
In conjunction with oil of turpentine, or ether containing hydrogen 


$82 COLOR REAGENTS AND INDICATORS. 


dioxide, it has been used to detect blood. Hydrocyanic acid turns 
blue a mixture of guaiacum and copper sulphate, and freshly pre- 
pared guaiacum-copper paper can detect very small quantities. 
On the other hand, a mixture of guaiacum and very dilute solution 


of potassium cyanide detects traces of copper by the blue colora- 
tion. : 


The tincture, as well as the paper, soon lose their sensitiveness 
by keeping, and must, in case of doubt, be tested with a specimen - 
known to contain ozone, or hydrocyanic acid, to see whether they 
yet promptly produce the blue color. It is best to prepare them 
fresh immediately before use. 


Clean pieces of the crude native resin are selected in preference 
to the refined (which has been exposed to air, etc., by the purify- 
ing proeess), or else the inner portion of a larger piece of guaia- 
cum wood (lignum vit). Three parts of resin (or 12 parts of wood) 
are digested with 100 parts of alcohol and the clear tincture de- 
canted; air and light being excluded, as far as possible. The paper 
is made by steeping into this tincture a paper free from wood pulp, 
as the latter often turns blue spontaneously. If copper is to be 
added, the paper is first dipped into the guaiac tincture, dried quickly 
to remove alcohol, and then dipped into a solution of one part of 
copper sulphate in 1,000 parts of water, and applied immediately 
to the mixture to be tested for hydrocyanie acid. 

Helianthin, also called Poirier’s Orange III, Methyl Orange or 
Tropzolin D, see dimethyl-amido-azo-benzol-sulphonic acid, page 20. 


INDIGO. Commercial indigo contains a variety of ingredients, 
of which indigo blue or indigotin, Cie Hio Nz O2, is the most im- 
portant. This is insolublein water and alcohol, soluble in concen- 
trated sulphuric acid, forming mono and disulphuriec acids. The 
alkali salts of the latter (sulph-indigotic acid), sold as indigo-car-. 
mine, are soluble in water. Indigo solution, as well of the acid as 
its salts, is of deep blue color, and is used as a qualitative reagent 
for nitric acid, chlorine and its oxygen acids, which oxidize and 
convert it into isatin-sulphonic acid, thereby changing the deep blue 
color into yellow. The solution is prepared either by dissolving 1 
part of indigo-carmine in 150 parts of water, or by gradually stir- 
ring 1 part of finely powdered indigo into 6 parts of fuming sul- 
phuric acid, contained in a vessel well cooled, to prevent the de- 
struction of indigotin by heat. The mixture is set aside for some 


days and then poured into 120 parts of water, well mixed and then 
filtered. 


This solution is also used in Mulder’s test for glucose in urine. 
The urine is colored by afew drops of indigo carmine, sufficient 


COLOR REAGENTS AND INDICATORS. 83 


sodium carbonate is added to render the mixture alkaline, and then a 
gentle heat applied. If glucose be present, the blue color changes 
first to green, then to a purplish red and at last to yellow. Shak- 
ing vigorously with air restores the blue color. 


It also serves as an indicator for volumetric determination of 
caustic alkalies in the presence of carbonates. The solution for 
this purpose is made by treating 1 part of indigo with 6 parts of 
fuming sulphuric acid for several days, just as above described, 
then adding calcium carbonate to neutralize, diluting with 10 parts 
of water and filtering. The blue solution is not affected by alka- 
line carbonates, but turns yellow with caustic alkalies. A few 
drops are added to the alkali solution to be tested, and acid is 
added until the yellow color changes to blue (Engel and Ville). 


An empirical standard solution for the volumetric determination 
of nitric acid in small quantities, especially nitrates in drinking 
water, is made by diluting solution of indigo (or of pure indigotin) 
so that it corresponds toa solution of pure potassium nitrate in 
water, containing 0.1607 grammes in 1 litre (=0.1 gr.H N Os). 
This solution is so adjusted that when 10 Cc. of the indigo solution 
are added to 10 Cc. of the nitrate solution, mixed with 10 Ce. of 
pure conc. sulphuric acid, while yet hot, the last drop must com- 
municate a permanent greenish-blue color. The results are re- 
liable only when equal conditions of temperature, rapidity of mix- 
ing, etc., are scrupulously observed in standardizing and in actual 
analysis. Each cubic centimetre of indigo solution used to pro- 
_ duce the permanent color indicates 0.1 milligramme of H N Os. 
- Others make standard solutions of different strengths: 1.8724 
grammes of K N Osto1 litre,.each Cc. corresponding to 1 Mgr. 
Ne Os (Marx, Trommsdorff, etc.); or 0.0962 gr. K N Os = 0.06 gr. 
HN Os in 1 litre (Mayrhoffer). 


LACMOID, Ciz Hy N O4<. A resorcin derivative, owing its name 
to its similarity to litmus (lacmus), which, however, it greatly ex- 
ceeds in delicacy. It is made by gradually heating to 110° C., on an 
oil bath, a mixture of 20 parts of resorcin (meta-di-oxy-benzol) with 
1 part of sodium nitrite and 1 part of water, contained ina capa- 
cious flask. A violent reaction ensues, during which ammonia is 
evolved and the color changes from yellow to blue. The mass 
fuses, and, after cooling, is dissolved in a small quantity of water. 
To the blue solution hydrochloric acid is added, which precipitates 
the lacmoid; this is separated on a filter, washed and dried, 
forming a red-brown, friable mass. It dissolves readily in alco- 
-hol, slightly in water, with a deep wine-red color, which is changed 
to blue by alkalies, and restored [to red by acids. It is a delicate 


84 COLOR REAGENTS AND INDICATORS, 


indicator for the hydrates, arsenites and borates of alkalies and 
alkaline earths and for inorganic acids. Solutions of zinc, cupric 
and ferric chlorides and sulphates, which redden litmus, leave lac- 
moid unchanged, unless they contain free acid. The solution is 
made by dissolving 1 part of lacmoid in 200 parts of dilute alcohol. 
Paper is impregnated with a still weaker solution. One drop of 
ammonia water in 5 litres of water suffices to produce the blue 
color (Traub and Hock). 


LITMUS or LACMUS. In commercial litmus there are con- 
tained azolitmin, erythrolitmin, spaniolitmin and erythrolein, 
combined with ammonium, potassium and calcium, and mixed with 
a considerable amount of gypsum, carbonate of calcium, etc. For 
very sensitive work azolitmin is isolated and its pure solution used. 
See page 47. Most of the other ingredients which interfere with 
delicate reactions may be removed and a good solution obtained by 
exhausting coarsely powdered litmus with boiling strong alcohol, 
so dissolve out the erythrolitmin. The residue, in which alkalies 
still preponderate, is then digested with an equal weight of water, 
and the solution drained off. This may be used for making ordi- 
nary blue litmus paper, but is too alkaline for delicate indications. 
The residue_is now digested with five parts of boiling water, and 
the filtered solution, which contains mostly azolitmin, is preserved 
in wide-mouth bottles, closed with a plug of cotton, so as to ex- 
clude dust but admit air, for in closely stopped bottles the solution 
soon deteriorates. 

To make blue test paper, unsized white paper, free from wood 
pulp, but not too porous, is dipped into the solution, and dried by 
suspending on strings of clean twine. For red paper a very small 
quantity of hydrochloric acid is added to the solution before dip- 
ping, so as to barely turn the color red. 

Litmus solution and paper turn blwe with alkalies, red with acids 
and many metallic salts. By lamplight the color change is not 
easily observed, unless the yellow sodium flame be used. Carbonic 
acid gives an intermediate violet color, dicarbonates do not affect 
the color. Hence, it is suitable for titration of the hydrates 
of alkalies and alkaline earths, alkaline silicates and arsenites, and 
for free sulphuric, hydrochloric, nitric and oxalic, somewhat less 
for acetic acid. In the titration of carbonates heat must be called 
in aid to decompose dicarbonates and expel carbon dioxide. 


LOGWOOD and HH#MATOXYLIN, Cis Hu Os. An aqueous 
solution of hzematoxylin is used to detect alum in bread by assum- 
ing a blue color. Also, in the titration of the carbonates of alka- 
line earths or other alkalies, with which it turns of a violet-blue 


COLOR REAGENTS AND INDICATORS. 85 


color, which acids change to yellow. Instead of the solution of 
pure hematoxylin, the yellow inner part of a larger piece of log- 
wood may be extracted with pure boiling water. The violet solu- 
tion is turned yellow by a drop of very dilute hydrochloric acid. 

_ Paper, previously freed from lime by dilute acid and washing, is 
stained yellow with this solution and forms a delicate indi- 
eator for ammonia, which turns it blue or blue-black, also for other 
alkalies. It must be preserved in closely stoppered bottles. 


MALVA. The petals of malva rosea and other dark red varieties 
yield to dilute alcohol a color similar to, if not identical with that 
of georgina, which turns green with alkalies, red with acids. They 
are often used for fraudulent manufacture of red wine. 

Mesityl-quinone is a rather improper name for a substance whose 
yellow solution in ether is colored violet by alkalies. 

Methyl-orange, the same as Helianthin, Tropeolin D, or Orange 
Ill. See Dimethyl-amido-azo-benzol-sulphonic acid, page 78. 


METHYL-VIOLET or Pentamethyl-parafuchsin, Cig Hiz N3 (C Ha)5- 
H Cl, is made by oxidation of dimethyl-aniline with cupric nitrate 
and sodium chloride. It forms crystals of gold-green lustre, easily 
soluble in alcohol and in water with violet color. Addition of a 
small quantity of a mineral acid changes the color to blue, a larger 
amount to green. In very dilute solution it serves in clinics to de- 
tect traces of hydrochloric acid in gastric juice. It belongs to the 
group named “‘basic colors,” by Ehrlich, and is used for staining 
of micro-organisms, urinary casts, etc. 

It also serves to detect fusel-oil in spirits. The alcohol is mixed 
with an equal volume of ether,and then diluted with sufficient 
water torender the ether insoluble. The ethereal layer floats on 
top and holds the fusel-oil (amyl alcohol) in solution. It is then 
separated and thoroughly shaken with a solution of 1 part of 
methyl violet in 100 parts of water, to which enough of very dilute 
(2%) hydrochloric acid has been added to render it green. The 
mixture is poured into a graduated cylinder, and the ether left to 
evaporate spontaneously, so as to concentrate the solution of fusel- 
oil. As soon as the ether has evaporated, so as to contain 2% of 
amyl alcohol a blue color will be communicated to it, and by using 
a measured volume of spirits the quantity can be determined 
(Uffelmann). If bile be present in urine and a few drops of the 
solution of methyl-violet are added, the color turns a carmine-red 
(Paul). As acetic acid does not change its color, the presence of 
even minute quantities of mineral acids in vinegar may be detected 
‘by the blue color of a dilute methyl-violet solution when a drop of 
adulterated vinegar is added to it. 


6 


86 COLOR REAGENTS AND INDICATORS. 


Nessler’s test for the colorimetric determination of ammonia is 
an alkaline solution of mercuric potassium iodide. See Mercury 
and its Compounds. 


p NITROPHENOL, Ce Hs.N O2 OH (1:8), colorless crystals, sol- 
uble in much water. The color is turned yellow by alkalies ; hence, 
its occasional use as indicator. Prepared by gradual addition of 1 
part of phenol to 6 parts of ice cold dilute nitric acid of spec. gr. 
1.12 (20%). A dark oily liquid separates, which consists of ortho 
and para-nitrophenol. These are separated by distilling with 
superheated steam at 214°C., when the ortho-compound distills 
over while the para-nitrophenol remains as residue, and is further 
purified by converting into the yellow sodium salt, crystallizing, 
separating by acid and distilling. 


ORANGE PEEL. An ethereal tincture of fresh orange peel be- 
comes colorless with acids and bright yellow with alkalies ; itmay, 
therefore, in case of necessity, serve as indicator (Bouchardat). 

Petri and Lehmann’s indicator is made by mixing 5 Ce. liquid 
phenol with 5 Ce. conc. sulphuric acid, adding to it, drop by drop, 
a solution of 1 gr. potassium nitrite in 20 Cc. concentrated sul- 
phuric acid, and heating to 80° C. until the color has become a 
dark blue-violet, and continuing the heat for some time after. 
The mixture is then poured into two litres of cold water, when the 
indicator separates as a violet insoluble mass. This is washed, dis- 
solved in ether, the solution filtered and the ether distilled off. 
The residue is dissolved in alcohol. With dilute acids the color is 
orange-red, with alkalies, violet-blue. Concentrated sulphuric acid 
turns it blue. . 


PHENACETOLIN, introduced by Degener for the purpose of de- 
termining at a single titration the amount of hydrate of alkalies or 
alkaline earths and that of their carbonates. The indicator is pre- 
pared by heating for several hours 20 parts of conc. sulphuric 
acid with 17 parts of phenol and 12 of glacial acetic acid, untila 
resinous looking residue remains. This yields to boiling water a 
brown solution of phenacetolin, while a greenish mass remains 
undissolved. The filtered solution may be used directly or evapo- 
rated to dryness for preservation. It is more soluble in alcohol 
than in water. The solution, when strongly diluted, is rendered 
pale yellow by alkaline hydrates, deep red by carbonates and golden 
yellow by acids. When a mixture of caustic alkali and carbonate ~ 
is titrated with sulphuric acid the specimen solution is tinted with 
a few drops of phenacetolin until pale yellow, as soon as enough 
acid is added to neutralize the hydrate, the color changes to red 
from the remaining carbonate, and turns a deep golden-yellow 


ee 


COLOR REAGENTS AND INDICATORS. 87 


with the first drop of acid in excess. The indicator also serves for 
alkaline silicates and arsenites. 


PHENOL-PHTHALEIN, C2 Hu O4. This is one of the most sen- 
‘sitive indicators known, on account of the difference of its color 
reactions, passing from deep purplish-red for alkalies to colorless 
for acids with great promptness and without intermediate tints. 
It is suitable for most acids and acid salts, for alkaline hydrates 
and carbonates, but is not adapted to ammonia or dicarbonates. 
It is prepared by mixing 10 parts of melted phenol with a solution 
of 5 parts of anhydrous phthalic acid in 4 parts of cone. sulphuric 
acid, and keeping them for a whole day at the temperature of 120° 
‘C. The fused mass is then poured into boiling water, and the ex- 
‘cess of phenol and of phthalic acid is removed by repeated change 
of boiling water. The undissolved residue is then dissolved ina 


‘dilute solution of caustic soda, filtered and precipitated by acetic 


acid, to which a little H Cl has been added. After 24 hours, the 
phenol-phthalein has subsided and is separated from the solution. 


When dried itforms a brownish-gray mass, which may be used in 


its as yet somewhat impure state, or purified by treatment with 
animal charcoal, ete. 


A solution of 1 part in 100 parts of alcohol, of about 50%, serves 
as indicator, of which 2 drops suffice to color 100 Ce. of liquid. In 
pure water it produces a slight milky turbidity, and remains color- 
less with most soluble salts and free acids, but turns a deep purp- 
lish-red on the slightest excess of alkaline hydrate or carbonate 
or caustic alkaline earths ; dicarbonates leave it colorless. 


m Phenylene-diamine. See page 78, m Diamido-Benzol in this 
article. 


PHLOROGLUCIN, Ce Hs (O H)s, isomeric with pyrogallol. It is 
used to detect minute quantities of free acid, especially for the 
clinical examination of gastric juice for free hydrochloric acid. 
For this purpose dilute solutions of phloroglucin and vanillin are 
mixed, and a drop or two added to an equal amount of the gastric 
juice. If even as little as 0.025% of HCl is present, the mixture 
slowly reddens as it dries(Guenzburg). The color change is not 
prompt enough to allowits use as volumetric indicator. It also 


serves to detect cane or grape sugar by turning an orange color 


when gently heated with them. In microscopical research it serves 
to stain woody fibre; it may also be used to detect wood pulp in 
paper, by staining it violet-red when brought together with it in 
acidulated alcoholic solution and heated; pure linen or cotton 
paper is not affected (Wiesner). 


6* 


88 COLOR REAGENTS AND INDICATORS. 


Phloroglucin may be prepared from phloretin, phloridzin, guer- 
cetin, maclurin and other substances by melting them with alkaline 
hydrates. Its principal source is the maclurin, obtained as a bye- 
product in the manufacture of the yellow dye from fustic (morus 
tinctoria). On a small scale it can be made by melting 1 part of 
resorcin with 6 parts of sodium hydrate, until the evolution of gas 
ceases and the fused mass has assumed a chocolate brown color. 
This is then dissolved in acidulated water, and the phloroglucin 
extracted by shaking with ether. The impure phloroglucin left on 
evaporation of the ether is heated to 100° C., to remove any un- 
changed resorcin, and then purified by repeated crystallization. 


Poirrier’s Blue, Cs B, a rosaniline derivative is sometimes used 
in alcoholic solution as indicator for even feeble acids, which do not 
respond to methyl-orange or phenol-phthalein. It turns red with 
alkalies, blue with acids. Borax manifests acid reaction with it. 

Rhubarb. Its tincture is used to stain paper, which turns yellow 
with acids, brown-red with alkalies. 

Rosolic acid, see page 19. 


SODIUM SALICYLATE, (Na C7 Hs Os)2 + He O, is used as an in- 
dicator for the titration of ferric salts by sodium hyposulphite. 
The violet color it produces with ferric salts turns colorless at the 
completion of the reduction (Haswell). 


The commercial salt is of sufficient purity. See also Salicylic 
Acid, page 19. 


TEST PAPERS. These are used in narrow strips for ascertain- 
ing neutrality, either by dipping into the liquid or by placing upon 
them a drop by means ofa glass rod. In some cases of volumetric 
analysis they are employed in preference to adding the color rea- 
gent to the solution. The paper used in their preparation should 
be unsized, so as to permit the ready entrance of the color to the 
fibre, yet not too loose in texture so as to absorb too readily. A 
pure, unsized rag paper, linen or cotton, is to be selected, free from 
admixture with wood pulp, which interferes with some reactions. 
Filter paper is mostly too porous in structure. The paper is cut 
into sheets of suitable dimensions, which are impregnated with 
the color solution (litmus, turmeric, red cabbage, phenol-phthalein, 
etc.), either by dipping or by the application of a soft flat brush. 
The moist sheets are hung up to dry onstrings of white thread, 
preferably in a dark room. After drying, they should be preserved 
in dark wrappers. It is very convenient to glue them together at 
one end before cutting into narrow strips, so as to have them in 
book form. 


COLOR REAGENTS AND INDICATORS. 89 


TETRA-HYDRO-ELLAGIC ACID, Cy Hio Og, called also hydro- . 
rujigallic acid, when melted with potassium hydrate, is converted 
into an isomeric body as yet unnamed, which is recommended by 
Oser and Kahlmann as a sensitive reagent, especially for carbon- 
ates, which react with it as if no carbonic acid were present. 

Hydrorufigallic acid is prepared by adding potassium perman- 
ganate to a solution of gallic acid in very dilute sulphuric acid. 
The product is extracted by shaking out with ether, evaporating 
and crystallizing from alcohol. One part of the crystals is fused 
with 5 parts of potassium hydrate until the mass turns red-violet. 
It is now saturated with sulphuric acid, which leaves an insoluble 
greenish-yellow substance, which is purified by crystallization 
from boiling water. It is now dissolved in dilute potassium hy- 
drate solution. The color, until neutralized, remains olive-green, 
but on the slightest excess of alkali becomes intensely red. When 
the red substance is diluted and accurately neutralized with sul- 
phuric acid it forms the indicator. Any excess of acid colors it 
yellow; alkalies, red. Not only the carbonates of alkalies, but of 
alkaline earths, also ferrous and manganous carbonate turn the 
color red, and, therefore, the indicator is valuable in titration of 

mineral waters, etc. 


TROPAEOLIN. This name is given by manufacturers to a va- 
riety of orange dyes, which are distinguished by the affixes: O, OO, 
900 I, OOO II, D and Y. All have been used as indicators and re- 
semble, more or less, the Zropaeolin D, which, under the name of 
Helianthin, Methyl Orange has been described in this chapter as 
Dimethyl-amido-azobenzol-sulphonic acid. ‘This appears to excel in 
delicacy, but the others are occasionally substituted, and produce 
mostly yellow tints with alkali, red with acids. 

Tropaeolin O, Chrysoin or Resorcin Yellow, is meta-dioxy-azo- 
benzol-sulphonic acid. 

Tropaeolin OO, or Diphenylamin Orange, is phenyl-amido-azo 
benzol-sulphonic acid. 

Tropaeolin OOO I, Mandarin or Orange II, is sulpho-azobenzol- 
beta-naphthol. 

Tropaeolin OOO II, or Orange I, is sulpho-azobenzol-alpha-naph_ 
thol. 

Tropaeolin Y is oxyazobenzol-sulphonic acid. 


TURMERIC or CURCUMA. The root of several varieties of 
curcuma contains curcumin, Cu His O4, which is soluble in alcohol 
with yellow color, changed to brown-red by alkalies. Other con- 
stituents, soluble in water, impair the delicacy of this color-change. 
Hence, the tincture is made by digesting one part of the powdered 


90 COLOR REAGENTS AND INDICATORS—COPPER AND ITS COMPOUNDS. 


root repeatedly with small quantities of water and rejecting the 
aqueous extract, and then digesting for several days with6 parts of 
alcohol and filtering. Itis seldom used directly, but serves to im- 
pregnate unsized paper, which should be dried and preserved in 
the dark. The color of turmeric paper is changed to brown-red by 
alkalies, and restored to yellow by acids, with the exception of 
boracic acid, which produces, even in the presence of hydrochloric: 
acid, a red color (after drying), which serves for the detection of 
borates. Turmeric paper is especially useful for titration with 
baryta water and for colored liquids, which would hide the color of 
an indicator added directly. Also for organic acids, especially 
citric, acetic, tartaric, lactie, oxalic and succinic, but hardly for 
the fatty acids of oils, etc. Brown-red turmeric paper serves to 
detect acid in alcohol. 


VANILLIN, Cg Hip Os, the methyl ether of protocatechuic aldehyd, 
forms the crystalline covering of vanilla beans. It is purified by 
recrystallization from boiling petroleum-ether. Dissolved in di- 
lute hydrochloric acid, it is used especially in microscopic research 
- as areagent for phenols, with which it produces ared color. Not 
all phenols react with equal promptness. A solution containing 
one part of vanillin, dissolved in 100 parts of alcohol, to which . 
100 parts of water and 600 parts of hydrochloric acid are added, 
reddens, in dry microscopic sections, only phloroglucin and orcin, 
while pyrocatechin, cumarin, resorcin, phenol, salicylic acid, pyro- 
gallol, etc., etc., are not affected, but require a more concentrated 
solution. 

Mixed with phloroglucin in dilute solution it serves to detect 
minute quantities of acid (hydrochloric acid in gastric juice). See 
phloroglucin above, page 87. 

Wurster's papers for ozonometry, see p amido-dimethyl-aniline, 
page 43. The tetra-methyl paper gives with ozone a blue color, the: 
di-methyl paper a red. 


Congo-red and Congo-paper, see Culor Reagents and Indicators, 
page 77. 


COPPER AND ITS COMPOUNDS. 
COPPER, Cu. 


Uses. In the metallic state copper is employed in qualitative 
analysis, in the form of bright, polished foil or wire, for the reduc- 


COPPER. 91 


tion of arsenic by Reinsch’s method, and for the detection of the 
salts of mercury, by reduction to metallic quicksilver. Occasion- 
ally it serves to detect nitric acid by its reduction to a lower oxide. 
It is also used to reduce stannic chloride to stannous. In elemen- 
tary organic analysis of nitrogenous bodies it is used to deoxidize 
nitric oxide and reconvert it to nitrogen. The form used for this 
purpose is either a bundle of copper turnings, a spiral of thin 
wire, a roll of thin foil or of wire webbing, or asbestus coated 
with fine copper (see page 47). For nearly all these purposes a 
good commercial article is sufficiently pure, and care must 
only be taken to have a perfectly clean surface, but in forensic ex- 
amination for arsenic the metal must be absolutely free from 
arsenic, and for the preparation of copper amalgam a perfectly 
pure metal is necessary. Atomic weight of Cu = 63.178. 

Tests. Iron, manganese, nickel, lead, silver, tin, bismuth, anti- 
mony and arsenic are often found in copper, when made by the 
furnace process, while the cement copper, prepared by precipitat- 
ing the solutions by iron, is only liable to contain the latter metal, 
and copper, made by the recently introduced electrolytic process, 
is absolutely pure, and should be used for chemical purposes to 
the exclusion of any other. 

To test for arsenic, a small quantity of copper is boiled with sul- 
phuric acid and the solution tested by Marsh’s process in a suit- 
able apparatus for evolving and igniting the hydrogen. To 
examine for other impurities, the metal is dissolved in nitric acid, 
in which it must leave no residue; a small portion of the solution 
is tested with sodium chloride or hydrochloric acid, and must give 
no precipitate (absence of silver and bismuth). The rest of the so- 
lution is precipitated by pure sodium hydrate, and the cupric hy- 
drate well washed on the filter. Filtrate and washings must give 
no precipitate with hydrogen sulphide (abs. of lead, zinc). The 
precipitated cupric hydrate is redissolved in dilute sulphuric acid, 
and, after the copper has been precipitated by electrolysis upon a 
platinum electrode, the acid solution must remain perfectly clear, 
and, on heating upon platinum foil, must leave no residue. 

PREPARATION. Either by electrolytic reduction of pure copper 
sulphate or by reducing pure cupric oxide by heating in a current 
of hydrogen. The wire, turnings or rolls of foil, for use in organic 
analysis, must be first heated in air to destroy organic dust, and 
then freed from the oxide superficially formed by ignition in hy- 
drogen. 

_ Copper Amalgam is sometimes used in connection with hydro- 
bromic acid for reducing sulphides, converting sulphur into hydro- 
gen sulphide. It is made by superficially coating pure copper in 


93 CUPRIC ACETATE—BUTYRATE. 


powder with mercury by rubbing it together with asmall quantity ~ 
of mercuric nitrate solution, washing the product and then incor- 
porating it, under hot water, with a proper amount of pure mer- | 
cury. 

CUPRIC ACETATE, Cu (C2 Hs O2)2 + He O. 


Uses. Neutral cupric acetate in aqueous solution is reduced by 
glucose at ordinary temperature, after some hours, to cuprous 
oxide. This occurs more rapidly if to the solution about 1% of 
acetic acid is added, and the mixture boiled for a short time and 
then set aside. These reactions serve to distinguish glucose from 
cane sugar, which does not reduce at ordinary temperature ; from 
dextrin, which does not reduce the boiled acidulated solution, and 
partly from milk sugar, which only reduces in very concentrated 
solutions (Barfoed). 

Mol. W. = 198.1338. 

Basie cupric acetate, or sub-acetate, Cu (C2 H3 O02. Cu(O H)e + 5 
He O, is proposed as a reagent for albuminoids, which, in presence 
of caustic alkalies, reduce it to cuprous oxide (Palm). 

Tests. When used for detection of glucose only, the commercial 
salt is of sufficient purity. In rare cases the purest salt is required: 
Pure cupric acetate forms opaque, deep green, clinorhombie erys- 
tals. At 15° C. it is solublein 13.4 parts of water, and in 135 parts of 
alcohol of spec. gr. 0.830, at 100° C. in 5 parts of water, at 70° C. in 
14 parts ofalcohol. Its aqueous solution should not yield a precipi- 
tate with barium chloride; nor, after addition of nitric acid, with 
silver nitrate. After ignition no soluble substance should be ex- 
tracted by water. A saturated aqueous solution of ammonium 
carbonate must dissolve it without residue. After precipitation 
by He S, the filtrate must leave no residue on evaporation. After 
Complete precipitation by potassium or sodium hydrate, the filtrate 
must yield no precipitate with HS. 

PREPARATION. By saturation of pure cupric oxide with pure 
acetic acid and crystallizing. The commercial salt may be puri- 
fied by repeated recrystallization from hot water or alcohol. Be- 
low 8% C. small rhombic crystals with 5 He O are formed, above 8 
C. the ordinary large clinorhombic crystals with 1 molec. H20O. 
If the solutions are kept at boiling heat basic acetate precipitates, 
while acetic acid volatilizes. 


CUPRIC BUTYRATE, Cu (C4 Hz O2)2 + 2 He O. 


~ Uses. To detect adulteration of oil of lemon by turpentine. 
Pure oil of lemon, when heated to 1722 C., dissolves a small quan- 
tity of dry cupric butyrate, forming a clear green solution; if oil of 














Cee a 
| REE 


| GAS BURETTE ana FIPETTE- 


CUPRIC POTASSIUM CARBONATE—CUPROUS CHLORIDE. 93 


turpentine is present, the mixture becomes turbid by separation 
of yellow cuprous hydrate (Heppe). 

PREPARATION. A concentrated solution of butyric acid in water 
is digested with an excess of pure cupric oxide or hydrate. The 
filtrate, on evaporation, forms monoclinic crystals. 


CUPRIC POTASSIUM CARBONATE, Cu K2(C Os)2 + 3 Hz O. 


Soldain’’s Reagent. 


Usss. This salt, dissolved in an excess of potassium dicarbonate 
solution, is used as a very delicate reagent for glucose, etc., espe- 
cially for the detection of invert sugar in cane sugar, or glucose in 
urine. It is reduced to cuprous oxide by dextro-glucose, levulose, 
milk sugar, tannic and formic acid, but remains unaffected by 
cane sugar, dextrin, starch, tartaric and uric acid, and by any of 
* the constituents of normal urine. In testing for invert sugar, 9.3 
gr. cane sugar are dissolved in sufficient water to make 15 Ce. and 
added to 50Cc. of Soldaini’s solution previously heated. The heat 
is then continued for five minutes, when the reduction will be 
complete if invert sugar was present in the amount of 0.5 milli- 
grammes or more. In testing urine not more than half a volume 
must be added to one volume of the reagent. As it keeps well 
without decomposition, it is one of the best reagents for use in 
clinics. 

PREPARATION. Fifteen gr. freshly precipitated basic cupric car- 
bonate, Cu C Os. Cu (O H)z (prepared by precipitating a solution of 
33.96 gr. pure crystals of cupric sulphate by an excess of sodium or 
potassium carbonate) are dissolved in a solution of 416 gr. of potas- 
sium dicarbonate in 1,200 Cc. of water, and then water added to 
make 1,400 Ce. If any portion remains undissolved, the solution 
must be filtered. 


CUPROUS CHLORIDE, Cue Cle. 


& 

Uses. In gas analysis cuprous chloride, in acid solution, serves 
to absorb carbon monoxide, acetylene, ethylene and phosphine, and 
in ammoniacal solution, also, some of the homologues of ethylene- 
This is either done by introducing into the absorption tube a 
ball of paper pulp soaked in a saturated solution of cuprous chlor- 
ide*in hydrochloric acid (Bunsen), or by placing this solution 
directly into the gas pipette (Winkler), or by using in the same 
manner an ammoniacal solution of cuprous chloride, which has 
greater absorbing power than the acid solution (Hempel). For the 
absorption of oxygen it is not so well suited as its action is too 
slow. 


94 CUPRIC HYDRATE. 


PREPARATION. Cuprous oxide is first made by heating a solution 
of cupric sulphate with sodium hydrate and glucose in some excess. 
This is added to concentrated hydrochloric acid in a well-closed 
flask until no more is dissolved. Or 10.8 gr. cupric oxide are mixed 
with 200 Cc. of concentrated hydrochloric acid, and the solution 
poured into a flask filled with copperwire or turnings, closed 
well to exclude air and digested until the solution becomes color- 
less. The ammoniacal solution is made by pouring the above 
colorless acid solution into a beaker containing 1,500 Ce. of water. 
The cuprous chloride, being insoluble in dilute acid, precipitates- 
After settling, the liquid is decanted, and the cuprous chloride, to- 
gether with 150 Cc. of water, is transferred to a flask closed with a 
doubly perforated cork and tubes, through which ammonia gas is 
passed until the salt is nearly all dissolved. This solution is di_ 
luted to 200 Ce. and preserved in a close flask. It is capable of ab- 
sorbing 6 Ce. of carbon monoxide. 


CUPRIC HYDRATE, Cu (0 H)z. 


Usrs. Cupric hydrate, either freshly precipitated or carefully 
preserved in close vessels, becomes, by the presence of glycerin, 
soluble in a solution of sodium or potassium hydrate, and serves to 
determine glucose by means of a standardized solution containing 
13.516 gr. of Cu (O Hein 1 litre, corresponding to 34.635 gr. of Cu 
S O, + 5 He Oin Fehling’s solution, and, like it, requiring 5 gr. of 
anhydrous glucose for complete reduction (Loewe). Cu(OH)2= 
97.0938. 


PREPARATION. As cupric hydrate, when well prepared and care- 
fully preserved, will keep unchanged for many years (Loewe), it 
may be madein some quantity and stored for use, or the requisite 
quantity may be freshly precipitated, when needed, from the corre- 
sponding amount of pure crystals of sulphate. To prepare it for 
keeping 50 gr. of cupric sulphate are dissolved in 200 Ce. of water, 
40 Cc. ammonia water added, and then a solution of 22 gr. pure 
sodium hydrate in 100 Cc. water. The precipitate is carefully 
washed and then dried over sulphuric acid and preserved in a 
close vessel. 

Loewe’s Solution is made by dissolving 138.516 gr. of cupric hy- 
drate (or the fresh precipitate from 34.635 gr. of Cu S O4 + 5 He O) 
by the aid of gentle heat in 500 Cc. water, to which 27 gr. pure 
glycerin and 24 gr. of sodium hydrate have been added. After 
cooling to 15° C. the solution is diluted to 1 litre. (Loewe directs 
the use of the 15.315 gr. hydrate produced by 40 gr. sulphate and 
dilution to 1,155 Cc., which gives the same proportions as above.) 


CUPRIC OXIDE. 95 


Haines’ Solution differs from the above, not only in strength, but 
also in not removing the alkaline sulphate produced by the pre- 
cipitation of the hydrate, It uses % gr. copper sulphate and 9 gr. 
potassium hydrate, dissolved in 100 gr. glycerin and 600 Ce. water. 


CUPRIC OXIDE, Cu 0. 


Uses. In organic analysis for the oxidation of H to HzO and of 
C to C Oz, in appropriate combustion tubes. It is used either in 
form of fine powder or of more compact granular masses, ob- 
tained by more intense ignition, or as asbestus coated with cupric 
oxide. 

In blowpipe work it serves to distinguish the halogens present 

in minerals or salts by the color communicated to the outer flame, 
when they are heated in the reducing flame with a microcosmic 
bead saturated with cupric oxide—chlorine, blue; bromine, bluish- 
green; iodine, yellowish-green (Berzelius). It is also used for con- 
verting the sulphides of arsenic, antimony and tin into their high- 
est oxides, by boiling their solutions in sodium sulphide with 
cupric oxide, which is thereby changed to cuprous sulphide (Berg- 
lund). Cu O = 79.188. 
Tests. Cupric oxide must not yield anything to boiling water. 
When heated to a red heat no vapor must be given off, either of 
sulphuric, sulphurous, selenous, nitrous, carbonic or other acids, 
which sometimes are due to dust or vapors finding their way into 
open vessels when carelessly kept, or to imperfect ignition. When 
prepared in the dry way the fine powder is deep black and of 
sandy feel, the compact variety grayish-black and quite hard. 
That, prepared in the wet way, has a brown-black color. 

PREPARATION. For the purposes of organic analysis, cupric 
oxide is generally made by dissolving copper in nitric acid and 
heating the dried nitrate to a red heat, while occasionally stirring 
the mass with a glassrod, until no more nitrous vapors are per- 
ceptible. After just sufficient cooling to permit handling, the 
oxide is ground in a clean, hot wedgewood mortar, sifted through 
a sieve of copper wire, and the fine powder carefully preserved 
from dust and vapors in closely stopped bottles. The coarser par- 
ticles are reheated ata higher temperature to form the compact. 
variety used in the combustion of more volatile substances. 

Asbestus is coated, either by sprinkling with the fine powder, 
or better, by soaking in a concentrated solution of cupric nitrate 
and heating to red heat. For desulphuration the fine powder ob- 
tained as above may be used, or else it is prepared in the wet way 
by protracted boiling of a solution of pure cupric sulphate with a 
small excess of pure sodium carbonate, until the precipitate has 





96 CUPRIC SULPHATE. 


all been converted into oxide, then thoroughly washing and ie 
ing at 160 C. 


CUPRIC SULPHATE, Cu S 01+ 5 H20 


Usrs. Cupric sulphate serves to detect bromides by forming 
with them, on addition of acid, ared cupric bromide. A solution 
of 1 part of cupric sulphate and 2} parts of ferrous sulphate pre- 
cipitates iodides, as white cuprous iodide, from neutral solutions. 
In conjunction with sulphurous acid it serves to detect sulphocy- 
anates in gas waters, etc., by a precipitate of white cuprous sul- 
phocyanate. It is also used for precipitation of alkaline ferrocy- 
anides, producing a deep brown-red cupric ferrocyanide; some- 
times an empirical copper solution is used for their titration 
(Hurter). Ina solution made slightly alkaline it forms with arsen- 
ous acid a bright yellowish-green, with arsenic acid a greenish- 
blue precipitate. It is also used for the detection of glucose by 
Trommer’s test. On adding}a small amount of cupric sulphate to 
the solution containing glucose, maltose, cellulose, lactose, invert 
sugar, etc., and then an excess of potassium or sodium hydrate; 
_ the precipitate of pale blue cupric hydrate at first formed is redis- 
solved with a deeper blue color, and, on heating, yellow cuprous 
hydrate separates, which by continued boiling is converted into 
the red cuprous oxide. Care must be taken to use no more cupric 
sulphate than can be reduced by the glucose, otherwise the sur- 
plus will form black eupric oxide and interfere with the reaction. 
If glucose is to be detected in urine, albumen must first be coagu- 
lated by heat, and turbid urine must be filtered and, if necessary, 
clarified by subacetate of lead. Chloroform, chloral hydrate, 
tannin and other substances produce the same reaction. It also 
serves to detect C O in blood by the bright red color of the precipi- 

tate. Cupric sulphate is also used for the preparation of pure 
copper and some of its compounds, especially for making various 
volumetric solutions for the detection of sugars, among them 
Fehling’s, Barreswill’s, Pavy’s, Haines’, ete. Cu S Os-+ 5He O= 
248.797. 
, Anhydrous cupric sulphate is of a pure white color, but attracts 
water and becomes blue; it is employed for detecting the presence 
of water in alcohol, etc., and for the purpose of dehydration. 


Tests. Cupric sulphate forms large, deep blue, triclinic crystals, 


. aR eosuble: in 24 parts of water at 15° C., in 1 part at 100° C.; insoluble 





wcohol. Its acidulated aqueous aolution must, after precipita. 
I y by He S, yield a filtrate which leaves no residue on evapora- 
tion. If into its acidulated solution bright pieces of pure iron are 


CUPRIC TARTRATE. 07 


immersed, and, after complete precipitation of the copper, the 
liquid is filtered, then heated with a little nitric acid and precipi- 
tated by ammonia in slight excess, it must, after removing 
the ferric hydrate by filtration, yield no residue on evaporation 
and ignition upon platinum foil. For quantitative purposes only 
clean crystals must be selected, which have not become white by 
superficial loss of water of crystallization. 

' | PREPARATION. As it is very difficult to purify commercial sul- 
phate containing other metals (excepting iron), recrystallizing is 
not to be depended upon for obtaining pure material, and it is best 
to use pure metallic copper and dissolve it in pure sulphuric acid. 
By boiling in a suitable flask the sulphur dioxide evolved may be 
utilized for making sodium di-sulphite or solution of sulphurous 
acid. The solution of sulphate in the flask is filtered, freed from 
any remaining S Oz by heating with a little nitric acid and repeated 
crystallization, the first crystals forming being the purest. The 
pure dried crystals must be carefully preserved in well stoppered 
bottles to prevent loss of water. 


CUPRIC TARTRATE, Cu C4 Hi Oc + 3 He O. 


Usgs. In solution with alkaline hydrates for detection and volu- 
metric determination of sugars. The principal one of these is 
known as 

Fehling’s Solution, 
of which, however, a number of modifications exist. Itis so ad- 
justed that 1 litre is designed to be completely reduced to red 
cuprous oxide by boiling with 5 grammes of dextro-glucose, Ceé His 
Os. It is usually assumed that this reduction occurs most accu- 
rately when the glucose is used in 2% solution. Careful investiga- 
tions of Soxhlet, Degener and Allihn have shown that accurate re- 
sults are obtainable only when the solutions not only contain the 
same amount of cupric tartrate (36.702 gr. Cu Cs Hs Os + 2 H2O 
corresponding to 34.635 gr. CuS O4-+ 5 Ha O in 1 litre at 15° C.), but 
also the same amount of alkaline hydrate and tartrate, and when 
the same conditions of concentration of the glucose solution, 
rapidity of admixture and time of boiling are strictly complied 
with. By using a1% solution of sugar, 100 Ce. of Fehling’s solu- 
tion require for reduction: : 

0.4752 gr. dextrose, time, 2 minutes. 

0.5044 gr. levulose, time, 2 minutes. 

0.6756 gr. lactose, time, 6 minutes. 

0.7788 gr. maltose, time, 4 minutes. 

0 4940 gr. invert sugar (either from cane or milk sugar), time, 2 
minutes — 


93 CUPRIC TARTRATE. 


(Deyener states that by the use of 18 molecules of Rochelle salt 
and 6 mol. of alkaline hydrate, 6 mol. of cupric salt arereduced by1 
mol. of glucose.) 

Fehling’s solution, as usually prepared, easily deteriorates and 
deposits cuprous oxide, even at ordinary temperatures, and still 
more by boiling, even without any addition. To prevent this, Pavy 
adds ammonia. Others recommend to keep separate solutions of 
the copper sulphate and the alkaline tartrate and hydrate and to 
mix them in proper proportion immediately before use. It is 
best in every case where accurate results are required to make a 
preliminary test, using 10 Ce. of Fehling’s solution, and according 
to the results obtained to dilute the urine or glucose solution so as 
to contain near to 1%, and then repeat the titration with 10 Ce. 
(or more) of Fehling’s solution, adding rapidly to it nearly the 
whole quantity ascertained to be requisite, and then finishing as 
rapidly as possible by gradually adding the rest till the reduction is 
_ complete, The end-point is ascertained by the disappearance of the 
biue color, or, as this in many cases is not reliable enough, by separa- 
ting a drop of the hot mixture and ascertaining the presence or ab- 
sence of copper by ‘‘spotting” withsolution of potassium ferrocyan- 
ide, acidulated. with acetic acid. A very accurate result may be ob- 
tained by using for the final determination anumber of flasks contain- 
ing the same amount of Fehling’s solution. To the first one of these 
an amount of sugar solution is added, slightly less than that indi- 
cated by the preliminary test; to the next one a little more, and so 
on. After boiling, the clear liquid of the flasks is tested for copper 
by ferrocyanide. The true amount of sugar needed must be be- 
tween that used in that last flask giving the reaction and the first 
one failing todoso. Some prefer to heat the sugar solution with 
an excess of Fehling’ssolution, and to weigh the reduced cuprous 
oxide. 

_An addition of a few drops of solution of aluminium sulphate or 
calcium chloride or zinc chloride towards the end of the reduction 
facilitates the rapid deposition of the cuprous oxide and leaves the 
liquid clear, Cu C4 H4 O¢ + 3He O = 264.709. 

Tests. Fehling’s solution must, on boiling for 2 minutes, either 
alone or diluted with water, remain perfectly clear and show 
neither change of color nor the slightest red deposit. 

PREPARATION. Distelye 34.635 gr. of cupric sulphate, in clear 
_ erystals, in distilled water, and dilute to 600 Ce. at 15° C. (or at the 
temperature indicated on the flask), and preserve in a well-closed 
glass-stoppered flask. Then 173 gr. of Rochelle salt, K Na Cs Hg 
Os + 4 He O, and 125 gr. K O H (or 89 gr. Na O H) are dissolved in 
water, diluted to 500 Ce., and also preserved separately in a well- 








HARP ADA'’S SEPARATOR 


aun Cn aT US FOR FEHLING®* TEST. 





CUPRAMMONIUM COMPOUNDS. 99 


closed bottle. The water used for solution should be boiled before 
use to destroy any germs of fungi, which might attack the tartrate. 
To avoid deterioration the tartrate solution may be made only im- 
mediately before use. 

It is a useful precaution to ascertain the correctness of the titre 
of Fehling’s solution by actual trial with absolutely pure dextro- 
glucose, under the same conditions of concentration, time of boil- 
ing, etc., as are to be observed with the specimen to be tested. For 
its preparation, see Glucose. 

In Pavy’s modification of Fehling’s solution 400 Ce. of ammonia 
water, of 0.88 sp. gr., are used instead of water, and the whole in- 
gredients mixed and reduced to 1 litre. 

Instead of 173 gr. Rochelle salt, Schmiedeberg proposes to use 16 
gr. pure mannite. Degener precipitates the cupric sulphate by 
alkaline tartrate, and saturates with this a solution of caustic soda. 
Barreswill, whose solution is much used in France, uses cream of 
tartar, sodium carbonate and potassium hydrate to dissolve the 
same quantity of cupric sulphate as in Fehling’s solution. 


CUPRAMMONIUM COMPOUNDS, 


Copper forms a large number of compounds containing 2 or 4 
mol. of N Hs, according to the general formule: Salts of cupri- 
diammonium Cu (N Hs)e. Re; cupri-tetrammonium Cu (N Hs)4. 
Re; cuproso-diammonium Cuz (N Hs)2. Re; cuproso-tetrammonium 
Cuz (N Hs)4 . Re. Of these the following are used as reagents: 


CUPRI-TETRAMMONIUM HYDRATE, Cu (N Hs). (O Hp, 
Schwettzer’s reagent, used, especially in microscopical investiga- 
tions, to dissolve cellulose (cotton cloth, filterpaper, etc.). Itisa 
deep blue liquid, made by repeatedly letting strong ammonia 
water drip slowly through fine copper turnings packed into a small 
cylindrical percolator, air being freely admitted (Peligot). Or by 
dissolving pure cupric hydrate in ammonia water. It should be 


freshly prepared for use, as preservation gradually impairs its 
efficiency. 


CUPRI-TETRAMMONIUM SULPHATE, Cu (N Hs)4. S O4 + He 
O. This is used in watery solution for the same purposeas the 
hydrate. It also forms a precipitate of green cupric arsenite with 
arsenous acid. It is also used as Kieffer’s volumetric solution for 
determination of acids. 

The dry salt crystallizes in deep blue, rhombic prisms, soluble 


‘in 1.5 parts of water, which lose ammonia in air, and still more 
rapidly by heating. 


100 DIASTASE, 


It is prepared by dissolving 1 part of cupric sulphate in 3 parts 
of ammonia water. ‘To the filtered liquid6 parts of strong alcohol 
are added, causing precipitation of the crystals. They must be 
preserved in well-closed bottles. Kieffer’s solution is prepared by 
dissolving cupric sulphate in water, adding ammonia until 
the pale blue precipitate of cupric hydrate is redissolved, and 
then adjusting the titre by dilution with water, soas to correspond 
with either normal or decinormal hydrochloric (or sulphuric) acid. 
The formation of a pale blue precipitate indicates the end of the 
reaction. . 

CUPRI-TETRAMMONIUM CHLORIDE, Cu (N Hs)4 Cle + He O, 
is used for the quantitative determination of carbon in iron by the 
McCreath-Uligren method. In this process 50 Ce. of the cupram- 
monium chloride solution (containing 15 gr. of the crystals) are 
used for every 1 gr. of iron to be tested. The iron at first precipi- 
tates the copper, dissolving in its stead, but by stirring for several 
minutes the precipitated copper is redissolved, forming cupri- 
cuproso-tetrammonium chloride, while all of the carbon is left be- 
hind undissolved. This carbon is carefully collected in a small 
filtering tube, filled with asbestus or glass-wool, and washed -thor- 
oughly, first with water, then with dilute hydrochloric acid, and 
at last with water. The filtering tube is then transferred to a 
flask connected with suitable apparatus and the carbon is oxidized 
by means of chromic and sulphuric acid. The resulting carbon 
dioxide is absorbed in a Liebig’s potash-bulb and weighed. 

The reagent is prepared by dissolving 160 gr. of cupric oxide in 
450 Ce. of hydrochloric acid of spec. gr. 1.16. After solution and 
filtration the liquid is saturated with ammonia gas and left to crys- 
tallize. Of the blue octohedral crystals, of Cu (N Hs)4 Cls + He O, 
300 grammes are dissolved in water and diluted to 1 litre. 


DIASTASE. 


Uses. This ferment, contained in malt, has the property to con- 
vert starch into dextrin and maltose. By heating with dilute 
acid (inversion) and titration with Fehling’s solution, the amount 
of sugar, and, by calculation, that of the starch may be deter- 
mined. Itis principally used for determination of starch used in 
adulteration of food (sausages, etc.). 

PREPARATION. 5 gr. of ground malt are dipested at 80° to 40° 
C. for 14 hours in 50 Ce. water, filtered and used at once. 


Diazo-benzol-sulphonic acid, see sulphanilic acid, p 20. 
Dimethyl-para-phenylen-diamine, see p Amido-dimethyl-aniline, 
p. 48. 


ETHYL ACETATE, 101 


Dipheny!l-amine, see in chapter on Color Reagents and Indicators, 
p. 79. 
Dipterocarpus Oil. 

This oil, distilled from gurjun balsam, a substance closely allied 
to copaiba, is used to detect free mineral acids in presence of or- 
ganic acids; 1 part of the oil, dissolved in 30 parts of glacial acetic 
acid, does not change color on addition of organic acids, but with 
the smallest traces of sulphuric, hydrochloric or other mineral 
acids it turns first rose-red, then deep violet The color is not 
discharged by alcohol (Jortssen). . 


Hosin, see Color Reagents, page 79. 


' ETHERS. 


ETHYL ACETATE, Ce H;. O02 Hs Oz. 
Acetic Hther. 


UsrEs. As a solvent of chloral hydrate, which it extracts from 
animal fluids in either acid or neutral solution. Also for the 
separation of alkaloids from solutions made alkaline by sodium 
carbonate. For this purpose it must be free from admixture with 
alcohol. An equal volume of the alkaline liquid containing the 
alkaloid and of acetic ether is thoroughly shaken together, and, 
after separation, the ethereal layer containing the alkaloid is re- 
moved. To itacidulated water is added, which renders the alka- 
loid salt insoluble in the ether, but soluble in water. For purifica- 
tion the process is repeated. It is especially applicable to mor- 
phine, strychnine, brucine, etc., less so to the cinchona alkaloids 
(Bar foed). 

Tests. Pure acetic ether is a colorless, volatile liquid of 
fruity odor; specific grav. at 0° C. = 0.9051, at 15° C. =0.8981; it 
boils at 72.782 C. It is miscible in all proportions with alcohol, 
ether and chloroform. At 17.502 C. 1 part requires 17 parts of 
water for solution; while 28 parts of acetic ether dissolve in 1 part 
of water. Its reaction with test papers is neutral, when well pre- 
served from air and light, otherwise it is liable to contain free 
acetic acid. For analytical purposes the presence of alcoholis 
especially to be guarded against; hence, when 10 Ce of the ether 
are shaken with an equal volume of pure water ina graduated 
cylinder; well-stoppered, and set aside to separate the upper ethe- 
real layer, must, at 17.5° C., occupy a volume of at least 9.3Cc. A 
greater shrinkage from solution in the water indicates too much 
alcohol. 


102 ETHYLIC ETHER. 


PREPARATION. To a mixture of 26 parts of conc. sulphuric acid 
with 12.5 parts of 94% alcohol 20 parts of anhydrous sodium ace- 
tate are gradually added and the mixture distilled on a water-bath. 
The product is purified by shaking at first with some dry sodium 
carbonate, then with fused calcium chloride, and, lastly, redistil- 
ling below 76° C. 


ETHYLIC ETHER (Cz Hs)2 O. 


UsEs. Pure ethylic ether, usually called ether, is used as a sol- 
vent for a variety of substances, inorganic and organic, among 
them iodine, bromine, phosphorus, sulphur, perchromic acid, 
lithium chloride, fats and resins, salicylic, benzoic and other acids, 
chloral hydrate, glucosides and alkaloids. Some of them may bg 
recognized by the characteristic color of the solution. Occasion- 
ally, ether is added to prevent the solution of portions of the pre- 
cipitates in the mixture in which they are produced, e. g., ammo- 
nium platinic chloride. Mixed with absolute alcohol it serves to 
extract and separate lithium from other alkaline chlorides. Mixed 
with alcohol and ammonia it forms Prollius’ mixture for alkaloid 
assays. 

Tests. For most analytical purposes the stronger ether U. S. P. 
is sufficient, but some require pure absolute ether. This is a color- 
less, volatile liquid, neutral to testpapers; does not change the 
color of white anhydrous cupric sulphate to blue; does not reduce 
a cooled mixture of sulphuric acid and solution of potassium di- 
chromate to green chromic alum inthecold. It does not dissolve 
aniline violet; hence, a color communicated indicates alcohol. If 
entirely free from water, the admixture of an equal volume of car- 
bon disulphide does not render it turbid. It boils at 34.97° C.; its 
spec. gr. at 17.52 C. is 0.7185. 

Pure officinal ether (xther fortior, U.S. P.) has spec. gr. 0.725 at 
15°C. It contains 94% wf absolute ether, the remainder being al- 
cohol and some water. It boils at 87° C.; hence, the average heat 
of the human body (87° C.) suffices to boil it, when held in the 
hand in a test-tube in which a few fragments of glass have been 
added to the ether. 

When 10 Cc. of this ether are shaken with 10 Ce. of glycerin ina 
graduated cylinder the ethereal layer must, after the separation, 
occupy no less a volume than 8.6 Ce. Like the absolute, it must be 
strictly neutral to testpapers. 

Ether is sometimes adulterated with benzin (petroleum ether). 
To detect its presence 5Ce. ether are mixed in a graduated cylinder 
with 10Ce. conc. sulphuric acid. If pure, the ether will form with the 
acid a clear uniform liquid; if benzin be present it will float on top, 


diesel 


ETHYLIC ETHER—FLUXBES. 103 


and may be measured and, after separation, identified by dropping 
into it a crystal of iodine, which, in benzin, dissolves with violet 
color; in ether, with brown. 

When solution of potassium iodide is added to pure ether no 
iodine is liberated (absence of hydrogen dioxide or ozone); potas- 
sium hydrate must not produce a yellow or brown color (abs. of 
aldehyde). 

PREPARATION. A mixture of five parts of pure, strong alcohol 
with nine parts of concentrated sulphuric acid is kept in a leaden 
(or glass) still at a temperature between 130° and 145° C., alcohol 
being from time to time added, so as to keep a constant volume of 
the liquid within the still. If the limits of temperature are strictly 
maintained only ether and water distill over; at lower temperature, 
alcohol; at higher, sulphur dioxide and ethylene are carried into 
the condenser. The product separates into two layers; the upper, 
containing ether, with some alcohol and water, is removed, agi- 
tated with calcium hydrate and rectified by repeated distillation, 
the fractions containing most alcohol and water being separated. 

For obtaining absolute ether the alcohol is removed by repeated 
washing with water, and the water by digesting with anhydrous 
calcium chloride and freshly burnt lime and finally redistilling. 

Prollius’ mixture is made by mixing 70 Ce. alcohol of 94% with 
30 Ce. of ammonia water of 28%, and enough of stronger ether to 
make 1 litre. A modification of this adds from 250 to 800 Ce. chloro- 
form and lessens the ether by an equal volume. 


Ethyl Orange, see Color Reagents, page 80. 

EHupittonic Acid, see Color Reagents, page 80. 

Fehling’s solution, see Cupric Tartrate. 

Fernambuco wood, same as Pernambuco, see Brazilwood, page 58. 
Flavescin, see Color Reagents, page 80. 

Fluorescein, see Color Reagents, page 80. 

Fluorspar, see Calcium Fluoride, page 64. 


2e2-- KLUXES. 
_These are agents used in the dry (docimastic) assay, which are 
added to the ores for various purposes. Some act as solvents of 
the impurities (gangue) accompanying the metals, converting them 
into fusible slag, such as powdered glass, quartz, kaolin, borax, 
microcosmic salt, or sodium, potassium and calcium carbonate, 
fluorspar, kryolite, litharge, etc. Others serve to reduce oxides, 


7* 


104 FLUXES. 


such as charcoal mixed with alkaline carbonates, black flux, potas- 
sium cyanide, etc. Others are used to oxidize, as saltpetre and 
litharge; some of them also decompose sulphides and separate the 
metal; some serve to concentrate the metal or extract it from the 
ore by alloying with it, as metallic lead, etc., or to volatilize, as 
ammonium salts. Others form a cover over the fused ore to ex- 
clude air, as sodium chloride, glass, ete. 

Most of these reagents are described under their respective head- 
ings in other portions of this work, while a few special mixtures 
find their place here. 


BLACK FLUX jis a mixture resulting from the deflagration of 
crude cream of tartar (argols) with a portion of saltpetre not quite 
sufficient to oxidize all of its earbon. It is used as a reducing 
agent in the assay of ores of lead, copper, tin, bismuth, nickel, 
zinc, etc. It is prepared by deflagrating in a red hot crucible, 
placed under a well drawing flue to carry off the gases, a mixture 
of saltpetre and argols varying in proportion. For very active re- 
duction three parts of cream of tartar are mixed with one part of 
nitre. When less active reduction is desired, only 2.5 or even 2 
parts of cream of tartar are used. The mixture, before deflagration, 
is called raw flux. 

As asubstitute for black flux some use a mixture of one part of 
starch or wheat flour, with from 2 to 5 parts of potassium or 
sodium carbonate, according to the more or less active reducing 
properties required. 


GRAY FLUX. Is made like black flux from a mixture contain- : 
ing 2 parts of nitre to 3 of cream of tartar. Its reducing property 
is much smaller than that of black flux. 


WHITE FLUX. In this the amount of saltpetre used is from 
1 to 2 parts to1 part of cream of tartar, so that no more unoxidized 
carbon remains or even some undecomposed nitrate remains to act 
as an oxidizer. Itis prepared like the preceding. 


GLASS. Finely powdered crown-glass, free from lead and ar- 
senic, is used either to form a protective cover, or as a solvent of 
basic ingredients of the ores. Its fusing point should be between 
those of borax and of fluorspar at about 1200° C. As it acts by the 
union of its silicic acid with the bases of the ore, it should not con- 
tain less than from 60 to 70% of Si Ox. 

In its stead powdered quartz or silicic acid (see on page 19) is 
sometimes used. 

For other fluxes see the articles Calcium Fluoride, Carbonate and 
Sulphate, Kaolin, Kryolite, Potassium Carbonate, etc., etc. 


et 


FUMING SULPHURIC ACID—GALLS +65 


Frochde’s Reagent, see Sulpho-molybdic Acid, page 12. 
Fuchsine, see Color Reagents, page 80. 


FUMING SULPHURIC ACID, 
Nordhausen Sulphuric Acid. 


Usss. This acid consists of a combination of sulphur trioxide, 
S Os, with sulphuric acid, H2zS Os. When these are in exact mole- 
cular proportion pyrosulphuric acid (disulphuric), He Se O7 results; 
when more S Osis present, it fumes in contact with moist air, and 
is called fuming sulphuric acid. 

It is used for dissolving indigo and for preparing organic sul- 
phonic acids; also for the solution of nitrogenous organic bodies 
and the conversion of their nitrogen into ammonia salt, according 
to Kjeldahl’s method ; also in gas analysis for the absorption of 
heavy hydrocarbon gases. 

Tests. In most cases the commercial acid is sufficiently pure. 
If desirable to test it qualitatively, the same method is employed 
as with ordinary sulphuric acid (page 22), great caution being 
necessary in diluting the acid. For quantitative analysis of its 
sulphur trioxide the volumetric method may be used; the speci 
men is weighed in a very small flask, this is carefully set up into a 
beaker, whose bottom is covered with water, insufficient to reach 
the neck of the little flask; the beaker is covered and left to stand 
for several days, so that the acidin the flask may first very gradually 
dilute itself, by attracting moisture, before an attempt is made to 
mix it with more water for proper dilution. 

PREPARATION. On the large scale, fuming sulphuric acid and 
sulphur trioxide are made by the dry distillation of ferrous sul- 
phate or acid sodium sulphate. On the small scale, it may be 
made by mixing pure concentrated sulphuric acid with sulphur 
trioxide (now easily obtainable in the market),or by adding to it 
phosphorus pentoxide sufficient for dehydration. See Sulphur Trt 
oxide. 

Furfurol, Cs Hs O2 (pyromucic aldehyde), is occasionally used to | 
detect urea, which is colored violet by addition of a saturated aque- 
ous solution of furfurol, followed by hydrochloric acid. It is ob- 
tained as a bye-product of the manufacture of garancin from 
madder; also by distilling one part of wheat or rye bran with one 
part of cone. sulphuric acid and three parts of water, and rectify- 
ing the distillate over sodium carbonate and chloride. 


GALLS. 


A 10% infusion of galls in water or dilute alcohol contains both 
tannic and gallie acid, and is sometimes used to detect iron, with 


108 GHLATIN—GLUCOSE. 


which it produces a greenish-blue to black color, according to the 
state of oxidation, and finally a black precipitate. It also serves 
as a precipitant of gelatin. When asmall amount of iodine solu- 
tion is added it indicates alkalies by an evanescent rose-red color. 
It is now seldom used, pure tannic or gallic acid being preferred. 


GELATIN. 


Uses. For removing tannic acid from vegetable extracts (detan- 
nation). Also in standardized solution for volumetric determina- 
tion of tannin. The aqueous extract containing the tannin is mixed 
with an equal volume of a saturated solution of ammonium chlor- 
ide, and the standardized solution of gelatin added till no more 
precipitate falls. The observation of this endpoint is facilitated 
by the presence of ammonium chloride and chromic alum, which 
cause the flocculent precipitate to separate rapidly and leave a 
clear solution. Dry gelatin also serves to collect alum from in. 
fusions of bread or flour adulterated with it. . 

PREPARATION. Ten parts of isinglass, or other pure variety of 
gelatin, are dissolved by the aid of heat in water, saturated in the 
cold with ammonium chloride, and containing 0.5 gr. of chromic 
alum. After the gelatin solution has cooled, enough of the ammon- 
ium chloride is added to make 1 litre. The titre is adjusted to cor- 
respond to pure tannic acid. 


GLUCOSE, Ce Hiz Oc. 
Dextro-glucose vr Grape Sugar. 


Usss. To adjust the titre of Fehling’s solutionand as areducent. 

Tests. By the polariscope. A solution containing in 100 Ce. 10 
gr. of anhydrous glucose, at 20°C. in a tube 200 Mm. long, turns the 
plane of polarization 10.6°, sodium light being used as illuminator. 
‘In an instrument graduated to read per cent of glucose, the per- 
centage of the solution must accurately coincide with the reading. 

PREPARATION. Mix 2,500 Ce. of 90% alcohol with 100 Ce. of most 
concentrated hydrochloric acid, keep the temperature at 45° C. and 
dissolve in it 800 gr. of pure cane sugar. In about two hours the 
inversion into dextrose and levulose is complete. Set aside in a 
cool place for several days. The dextrose (glucose) will then sep- 
arate in crystals, whileacid and levulose remain in solution. The 
crystals are drained on a glass funnel, washed with alcohol until 
all acid has been removed; then they are dissolved in hot alcohol 
(methyl alcohol is preferable) and recrystallized. The recrystal- 
lization is repeated once or twice, the product is then powdered 
and dried sharply at 1022C. Pure anhydrous glucose is the result. 





FRESENIUS and WiLL" 
APPR RATUS for CO, & Mn OQ, 





SLAMENTATION TUBE. | 





GE/SSLER'S CO, 
INDEX of POLARISCOPE APPARATUS. 
READING OFF 55° 






APPEARANCE af FIELO of VISIOM 
«a POLAPISCOPE, ~ 






LANDOLT’* 
SODIUM LANMEF: 


MITSCNERLICHM'S POLAPBRISCOPE a PENOMER EL. 


lh beled Chi NE 





GOLD—AURIC CHLORIDE. 10? 


Glyeerin, see Alcohols, page 28. For absolutely pure glycerin the 
following tests are added: After evaporation, at moderate heat, 
upon a slip of glass the microscope must show by transmitted light 
neither turbidity nor black or brown coloring of the spot occupied 
by the glycerin. A mixture of 3 Cc. each of glycerin and ammonia 
water (10%), heated to boiling in atest tube, must, after addition 
of 0.5 Cc. solution of silver nitrate, remain clear and colorless for 


at least 5 minutes. 
GOLD, Au. 


Uszs. Metallic gold is used for the preparation of gold chloride 
(aurochloric acid). Also in the docimastic assay, by Plattner’s 
method, of nickel ores or alloys, containing a small percentage of 
copper, for the purpose of preventing the slagging of the copper 
while nickel and arsenic, etc., are removed by oxidation. In thin 
foil it sometimes serves instead of copper for the recognition of 
mercury. 

Tests. Are made with its solution and are the same as those for 
gold chloride, as described in the next article. 

PREPARATION. Coin gold is dissolved in a minimum of cold nitro- 
hydrochloric acid (see page 15). The solution is set aside for seve- 
ral days to deposit all of its silverchloride. It is then decanted 
and precipitated with pure ferrous sulphate, dissolved immediately 
before use in boiled distilled water. The fine gold powder is per- 
mitted to settle in a warm place, the liquid is then poured off and 
the sediment repeatedly washed. It may then be used directly for 
preparation of gold chloride or fused with pure potassium nitrate 
and borax. 


AURIC. CHLORIDE, Au Cls + 2 H20; AURO-CHLORIC ACID. Au 
Cis. H Cl +4 He O. 
Gold Chloride. 


\ Usges. Aurochloric acid is used to detect tin by the precipitation 
of the purple of Cassius. The more neutral auric chloride is em- 
ployed in the analysis of alkaloids, many of which it precipitates 
from solution, forming with them double salts. In a solution of 
albumin acidulated with formic acid the addition, drop by drop, of 
a 1% solution of gold chloride and heating, produces, first, a rose- 
red, then a purple color, changing, on further addition of gold so- 
lution, to blue. 

Tests. A dilute solution, heated gently with some excess of ox- 
alic acid, must, after separating the metallic gold by filtration, 
leave no permanent residue on evaporation. Addition to a con- 
centrated solution of ammonium or potassium chloride must pro- 
duce no precipitate. 


108 HYDROGEN, 


PREPARATION. Aurochloric acid is made from the pure gold, ob- 
tained by precipitation by ferrous sulphate or oxalic acid and thor- 
ough washing. Itis dissolved in a minimum of pure nitro-hydro- 
chloric acid (see page 15), and, after solution, concentrated on a water 
bath, while a small amount of hydrochloric acid is added. The 
residue, on cooling, forms yellow crystals of Au Cls. HCl + 4 H2 0, 
which are dissolved in 30 parts of water. If the gold chloride, Au 
Cls, is to be made, the addition of H Cl is omitted and the evapora- 
tion conducted at a somewhat higher temperature (110° C.). The 
dry residue is either dissolved for use in 30 parts of water or crys- 
tallized by addition of water and evaporation at 100° C. A temper- 
ature of 185° C. completely decomposes auric chloride into aurous 
chloride and free chlorine. 


Guaiacum, see Color Reagents, page 81. 

Gurjun, see Dipterocarpus Oil, page 101. 
Hematoxylin, see Logwood in Color Reagents, page 84. 
Hydriodic Acid, see on page 7. 

Hydrobromic Acid, see on page 7. 


Hydrocerolignone, Cig His Oc, is recommended by Liebermann as 
a most delicate reagent for quinone. Even in very dilute aqueous 
solutions of quinone the addition of a few drops of alcoholic soiu- 
tion of hydroccerolignone produces at first an orange color, then a 
steel-blue precipitate of coerolignone. 

It may be prepared from ccerolignone by reduction with nascent 
hydrogen (boiling with zinc and hydrochloric acid). Ccerolignone 
separates when crude pyroligneous acid is mixed with potassium 
dichromate as a steel-blue precipitate, which is purified by dissolv- 
ing in phenol and precipitating by alcohol. 


Hydrochloric Acid, see on page 8. 

Hydrofluoric Acid, see on page 9. 

Hydrofluostlicic Acid, see on page 10: 
HYDROGEN, H, 


Usrs. For the preparation of pure metals by reducing metallic 
oxides. In the determination of copper as cuprous sulphide. In 
gas analysis for determination of oxygen by explosion. For the 
production of high temperatures by burning with oxygen in the 
compound blowpipe in the assay of refractory metals. 

Tests. Pure hydrogen, when burnt from a jet, does not produce 
any spots on a cold piece of porcelain held into the flame. The 
water condensed on the porcelain must have a perfectly neutral 
reaction; the products of the combustion passed into lime or baryta 
water must not render it turbid. A paper moistened with silver 
nitrate must not be blackened by the gas. 


HYDROGEN DIOXIDA, 108 


PREPARATION. In small quantities, for gas analysis, pure hydro- 
gen gas may be made by the electrolysis of very dilute, pure sul- 
phuricacid. Also by heating palladium which had previously been 
saturated with hydrogen at 100°; or by bringing pure zine and 
pure acid together in one of the compartments of a gasburette. 

On a somewhat larger scale, for reductions, pure, dry hydrogen 
gas is made by placing pure zinc and pure dilute sulphuric acid 
into a suitable gas generator, connected with a .series of tubes or 
flasks for purification; first, a simple wash flask to retain any par- 
ticles of acid carried over mechanically; then one filled with solu- 
tion of potassium permanganate, next with sodium hydrate, and 
lastly, with anhydrous calcium chloride, to remove moisture. For 
use in the compound blowpipe, the presence of carbon in zine, other- 
wise pure, does not interfere. 


HYDROGEN DIOXIDE, He Oz. 


Uszes. To oxidize, in alkaline solutions, the sulphur of metallic 
sulphides, sulphuretted hydrogen, or polythionates to sulphuric 
acid, which may then be determined as barium sulphate (Classen 
and Bauer) or volumetrically (Hliasberg), thereby also allowing 
the determination of chlorides, bromides and iodides, when He S is 
present. Also to detect titanic, molybdic and vanadic acid by col- 
oration of yellow to orange-red (Schoenn). Also in the analysis of 
nitro-glycerin and other nitro-compounds by oxidizing Ne Os to Ne 
Os (Hampe). For recognition of chromic acid and chromates by 
their conversion into a deep blue substance, whose composition is 
as yet unknown (usually called perchromie acid), soluble in ether. 

Tests. A solution of hydrogen dioxide is so liable to deteriora. 
tion by decomposition into water and oxygen gas that an estima- 
tion of its strength should be made by the depth of the blue color 
produced with potassium and dichromate solution. A small per. 
centage of free acid preserves it longer, but care should be taken 
that another acid should be used than that which is to be deter- 
mined. Hence, for determining sulphides it must not contain sul- 
phuric acid, nor hydrochloric, if chlorides are to be detected. For 
oxidizing the lower oxides of nitrogen, phosphoric acid might be 
added. The solution should leave no permanent residue on evapo- 
ration. 

PREPARATION. Pure barium dioxide, suspended in water, is very 
gradually added to an ice cold mixture of 1 part of pure sulphuric 
acid with 5 parts of water, the vessel being surrounded by ice and 
the mixture being constantly stirred until the acid is nearly neu- 
tralized. After filtration, the excess of acid is carefully removed 
by the addition of baryta water. The liquid is filtered again and 


110 HYDROXYLAMINE HYDROCHLORATE—IODINE. 


preserved in a cool dark place. It may be concentrated by freez- 
ing the water and decanting the concentrated solution. 

flydrogen Sulphide, see Hydrosulphuric Acid, page 10; also Bar- 
tum Sulphide, page 52. To free hydrogen sulphide from arsenic, 
hydrochloric acid in various states of dilution is used in a system 
of four wash bottles, the contents of which are kept at 60° to 70° C. 
The first has 1 part of hydrochloric acid with 2 parts of water; the 
second, 1:4; the third, 1:8; the fourth, distilled water. No rubber 
is used about the apparatus (Lenz). 


HYDROXYLAMINE HYDROCHLORATE, N H20H.H Cl, 


Users. For quantitative determination of silver, which is reduced 
to metal by hydroxylamine hydrochlorate and potassium hydrate 
from its haloid salts and their solutions in sodium hyposulphite 
(Lainer), Also to recognize aldehydes and ketones by converting 
them into isonitroso compounds (acetoximes), in which the group 
= C = O is replaced by = C= N — O — H (Negeli, V. Meyer). 

Tests. Hydroxylamine hydrochlorate forms transparent mono- 
clinic crystals, soluble in water and in alcohol. Absence of am- 
monium chloride must be shown by platinic chloride producing no 
turbidity in its solution. The salt melts at 151° C., and, on further 
heating, suddenly decomposes, leaving no permanent residue. 

PREPARATION. Pure nitromethan,C Hs.N Ocis prepared from 
silver nitrate and methyl iodide. This is mixed with dilute hydro- 
chloric acid in molecular proportion, and placed in stout glass 
tubes, sealed hermetically. These are placed into a suitable safety 
envelope and heated not to exceed 150° C. A solution of hydroxy- 
lamine salt and C O are formed. After opening the tubes the solu- 
tion is carefully concentrated by evaporation, the crystals are re- 
dissolved in hot absolute alcohol, and on its evaporation are care- 
fully preserved in opaque vessels. 


Indigo, see Color Reagents, page 82. 

Indol, Cs H7 N, is occasionally used to detect, under the micros’ 
cope, lignin in vegetable tissues, in paper, etc., by coloring it in- 
tensely red. It is, however, much inferior to aniline sulphate for 
this purpose. 


IODINE, I. 


Uses. In connection with potassium hydrate to detect, by the 
formation of iodoform ethyl, propyl, butyl and capryl alcohols: 
acetic, propionic and butyric aldehydes, quinic, meconic and 
lactic acids, methyl butyrate, methyl benzoyl and oil of turpentine 
(Lieben). ‘To detect metallic mercury in sublimates in glass tube 


IODINE. jii 


by conversion into Hg Iz. To detect bismuth by the blow-pipe test 
as scarlet oxyiodide. To detect tannic, gallic and pyrogallic acids 
by an evanescent purple-red color (Nasse). In gas analysis it is 
used to absorb carbon disulphide (Hiloart). To identify starch by 
its blue-black coloration, especially starch granules in situ under 
the microscope, iodine is used either as iodine-water, a saturated 
solution of iodine in distilled water containing about 0.014% of 
iodine, or as a solution in dilute alcohol, glycerin or potassium 
iodide solution. A solution of iodine in zine chloride, or of iodine 
in water, followed by concentrated sulphuric acid, colors cellulose 
blue. In volumetric analysis a solution of iodine and potassium 
iodide (mostly of decinorma] strength) is used with a companion 
solution of sodium hyposulphite (thio-sulphate) and starch solu- 
tion as indicator for a great variety of determinations. It per- 
mits the estimation of arsenic trioxide and arsenites, chlorine and 
hypochlorites, sulphites, hyposulphites, chromates, chlorates, 
manganese dioxide, etc. Also of acetone by the formation of iodo- 
form and measuring back the surplus of iodine, and of many 
other substances by either direct or indirect methods. It is also 
used to precipitate many alkaloids, forming with some of them char 
acteristic compounds. An alcoholic solution of iodine is some- 
times used to add to oils, with which some of the iodine unites, 
enabling a differentiation of the oils by measuring volumetrically 
the amount of iodine retained, which is expressed in per cents of 
the oil, and called the iodine-addition number (Hwb/). Atom. W. 
I = 126.559. 


Tests. When heated in a test-tube pure iodine completely vola- 
tilizes, showing no deposit of moisture at first, nor colorless crys- 


‘tals in its sublimate, nor leaving a trace of residue. Its solution 


in chloroform must be perfectly clear. To distilled water, recently 
boiled to expel absorbed gases, it should impart only a ight brown 
color (a deeper brown indicating presence of hydriodic acid, chlor- 
ide of iodine, etc.). To detect iodine cyanide, water saturated with 
iodine is shaken with pure carbon disulphide until all color of 
iodine is removed, and, after settling of the iodine solution in C Sz, 
a portion of the clear liquid is carefully decanted. In this a small 
granule of ferrous sulphate is dissolved, then a few drops of ferric 
chloride are added, and lastly some potassium hydrate. After di- 
gesting the mixture for some time it isacidulated with hydrochloric 
acid. A. blue precipitate of ferric ferrocyanide would indicate 
presence of iodine cyanide. After converting the iodine into silver 
iodide, ammonia water must not dissolve any portion of it. Hence, 
after filtration and acidulating with nitric acid, it must remain 


112 {RIDIUM-SODIUM CHLORIDE—IRON, 


clear. Perfectly pure resublimed iodine is now easily obtainablé 
from dealers. 

PREPARATION. Commercial iodine is powdered and heated to 
100° C. ona water-bath in a porcelain dish for about 15 to 20 min- 
utes. The vapor is either suffered to escape or condensed upon 
the bottom of a flask filled with cold water. This removes any 
iodide of cyanogen, which volatilizes at 45° C.and forms colorless 
crystals, adhering to the cold flask. All moisture is also driven 
off and chloride of iodine mostly decomposed or volatilized. After 
20 minutes the remaining iodine is thoroughly mixed with about 
five per cent of pure dry potassium iodide to decompose any re- 
maining chloride or bromide ofiodine. It is then returned to the 
porcelain capsule, which is closely covered with a clean glass fun- 
nel, and slowly heated on a sand-bath so as to sublime the iodine, 
which adheres in large crystals to the funnel. It must be carefully 
preserved in close vessels. 

Deci-normal solution ismade by adding 12.66 gr. of pure iodine 
to a solution of 18 grammes of pure potassium iodide in 900 Ce. 
water, dissolving by agitation, avoiding heat and filling up tol 
litre. 

See also Sodiwm Hyposulphite and Starch. 


IRIDIUM-SODIUM CHLORIDE, Ir Cl: .2 Na Cl + 6 H2 O. 


Uses. The aqueous solution of the black erystals of this salt has 
been used in the analysis of alkaloids, some of which it precipi- 
tates, while morphia is not precipitated by it (Planta). 

As pure metallic iridium only dissolves when in the state of min- 
utest subdivision, but is easily dissolved as alloyed with platinum 
and other metals, it is not advantageous to prepare its salts on 
the small scale; they are obtained as bye-products at the platinum- 
affineries and sold by dealers in a sufficiently pure state. 


IRON AND ITS COMPOUNDS. 


IRON, Fe. 


Uses. In the metallic state iron is used to detect copper by re- 
ducing it from its salts, showing a red film of metallic copper upon 
the iron. For this purpose any bright piece of sheet iron or wire 
is suitable. Minute traces of copper are detected by using a bright 
steel needle as electrode of a battery. In the wet assay copper is 
completely precipitated by pieces of iron wire placed into the 
acidulated solution. It is also used for the preparation of salts, 
for adjusting the titre of volumetric solutions of potassium di- 
chromate or permanganate. For this purpose the fine, soft wire 


sul 


FERRIC ACETATE—CHLORIDE. 113 


used by florists is sufficiently pure, when bright and freefrom rust. 
Fe = 55.913. 
Tests. The gas evolved from absolutely pure iron and pure di- 


_lute hydrochloric or sulphuric acid must be inodorous and not 


blacken a drop of silver nitrate placed on filter paper over the 
test-tube from which the gas is evolved. The solution resulting 
must be clear and without flocculi, nor must any part of the iron 
remain undissolved. It must not yield a precipitate with hydrogen 
sulphide. After precipitation of the solution, neutralized with am- 
monia, by ammonium sulphide, the filtrate must leave no residue 
after evaporation and ignition. 


FERRIC ACETATE, Fez (C2 Hs 02)6. 


Uses. When perfectly neutral ferric acetate in very dilute solu- 
tion is mixed with potassium sulphocyanate, no reddening Occurs 
from the formation of ferric sulphocyanate until free acid is added. 
Hence, the mixed solutions are employed to detect free acid (Mohr). 
Presence of sodium acetate interferes with the reaction. Ferric 
acetate is also used in the analysis of tannins, in the place of skin 
powder, to precipitate tannic acid. 

Tests. The solution must not contain free acid. When diluted 
so as to show only a faint yellow color, afew drops of potassium 
sulphocyanate solution must not produce a red color, until a drop 
of hydrochloric acid is added. The U.S. P. preparation is too 
acid to be used for this test. 

PREPARATION. 5.5 gr. of ferric chloride are dissolved in water 
and poured into ammonia water in slight excess, so as to precipitate 
the ferric hydrate completely. The precipitate is thoroughly 


- washed and dissolved in 3.5 grammes of glacial acetic acid without 


the aid of heat. The small residue left undissolved is filtered off 
and the solution diluted to 100 Ce. It should be carefully pre- 
served in a cool, dark closet. 


FERRIC CHLORIDE, Fee Cle + 12 He O. 


Uses. Asa group reagent for organic acids not precipitated by 
calcium chloride. It produces with succinates and benzoates 
brownish, with ferrocyanides blue, with tannates blue-black pre- 
cipitates; acetates, formates, sulphocyanates, pyrogallates and 
meconates are colored red, ferricyanides brown, gallates black, 
salicylates violet. Of organic bases it colors aniline red, mor- 
phine blue, while codeine, thebaine, papaverine and narcotine are 
left colorless, and narceine colored blue only after partial decom- 
position by heat. Thalline, even in minute traces, is colored 


114 FERRIC CHLORIDE. 


green by ferric chloride, antipyrine brown-red, etc.; phenol is col- 
ored violet, and, in aqueous solution, all phenols, aromatic oxy- 
acids, carbohydrates and alcohols give characteristic color reac- 
tions with very dilute ferric chloride, so that Landwehr proposes it 
as a general reagent for the presence of the hydroxy] group. In con- 
junction With ammonia very dilute solutions of ferric chloride color 
many organic sulph-hydrates a deep red-brown (Claesson). It is also 
used to decompose phosphates of alkaline earths, and to remove their 
phosphoric acid. In conjunction with potassium nitrite it serves 
to detect small quantities of hydrocyanic acid by converting it into 
nitroprusside, which is readily known by its reaction with alkaline 
sulphides (Vortmann). Mol. W. Fee Cle = 824.046. 

Tests. Ferric chloride must dissolve without residue in water 
or alcohol; it must be free from ferrous salt; hence, it must give 
with freshly prepared potassium ferricyanide solution a clear 
brown color, without shade of green or trace of precipitate. It 
must be perfectly neutral, so that when stirred with a glass rod 
dipped into ammonia water a permanent brown-red precipitate is 
formed. Absence of the nitrogen acids must be shown either by 
ferrous sulphate and sulphuric acid, or.after precipitation of the 
iron by ammonia, in the filtrate, by diphenylamine or pyrogallol 
and sulphuric acid. Absence of sulphates is shown by barium 
chloride. After precipitation of the iron by ammonia the colorless 
filtrate must not yield a precipitate with ammonium sulphide, nor 
leave, on evaporation, a permanent residue. After addition of an 
excess of ammonium acetate and boiling until the iron is com- 
pletely precipitated as basic aeetate, the filtrate must leave after 
evaporation, no fixed residue. After acidulation with hydro- 
chloric acid sulphuretted hydrogen must produce a pure white 
precipitate of sulphur, which volatilizes without residue. 

PREPARATION. Ferrous chloride is first made by gently heating 
in a large flask 1 part of pure, fine iron wire with 4 parts of hydro- 
chloric acid, of spec. gr. 1.16, until no more hydrogen gas is 
evolved. The solution is separated from the small excess of iron, 
and converted into ferric chloride by passing into it pure chlorine 
gas (the absorption being hastened by frequent agitation) until a 
drop taken out gives a pure brown color to a fresh solution of po- 
tassium ferricyanide. The excess of chlorine is now expelled by 
moderate heat and the solution placed under the bell glass of an 
exsicecator to crystallize. If wanted in solution it is diluted so that 
for 1 gr. of iron used 20 Ce. areobtained. The process of prepara- 
tion by the aid of nitric acid, as usually employed, yields a pro- 
duct from which the last traces of the oxides of nitrogen are diffi- 
cult to remove. 





FERROUS CHLORIDE—SULPHATE. 115 


FERROUS CHLORIDE, Fe Cle. 


Uses. Ferrous chloride, dissolved in strong hydrochloric acid, 
is used for the quantitative determination of nitric acid and ni- 
trates, according to Schloesing’s and other modified methods. Also 
for converting arsenic into the volatile As Cls, which is separated 
by distillation and its quantity ascertained (Beckurts). Occasion- 
ally, it serves in the separation of selenium. Mol. W. = 126.653. 

PREPARATION. Ferrous chloride is only prepared when required 
for instant use, as it can be preserved only with difficulty. Pure, 
fine iron wire is then dissolved in pure hydrochloric acid of such 
concentration as is suitable for the special work; the vessels in 
which the solution is made are filled either with hydrogen or car- 
bonic acid gas to prevent decomposition by atmospheric oxygen. 


Ferric dinitrosulphide is made, according to Hoffmann and Power, 
by adding a solution of ferric chloride or sulphate, drop by drop» 
to a mixture of equal parts of concentrated solutions of potassium 
nitrate and ammonium sulphide. The mixture is boiled for a few 
minutes, filtered while hot from the sulphur, and set aside to de- 
posit, on cooling, black, rhombic crystals of ferric dinitrosulphide. 
These are dissolved in 10 parts of water. 


Ferric Ferricyanide is made only when needed by mixing the 
freshly prepared solution of potassium ferricyanide with ferric 
chloride. The brown solution is reduced more or less rapidly 
by morphine and many other alkaloids and by most ptomaines, 
so that adeep blue precipitate of ferric ferrocyanide (Prussian 
blue) or of ferrous ferricyanide (Turnbull’s blue) is formed. 


Ferric Oxide, Fez Os, is used in the docimastic assay of copper. 
The commercial article is sufficiently pure. 


Ferric Sulphate, Fe2(S O4)3, and ferric ammonium sulphate, Fee 
(S O43. (N Hae S Os + 24 He O (ferric alum), are sometimes used 
in 10% solution as indicators in the titration of silver by ammo- 
nium rhodanate. Freedom from chlorine is the only requisite of 
purity. 

FERROUS SULPHATE, Fe S 01+ 7 H20. 

Ussrs. The tendency of ferrous sulphate to change to ferric salt 
makes it a powerful reducent. As such it serves to precipitate 
gold; to recognize nitric acid by reducing it to N O, which dis- 
solves in the remaining solution of ferrous sulphate with a dark- 
brown color. By heating this brown color disappears readily. 
A similar reaction is produced by acids of selenium, but then, heat- 
ing does not cause the brown color to disappear, but rather to be” 
come more intense, and finally change to ared precipitate of se- 


116 FERROUS AMMONIUM SULPHATHR. 


lenium. It is also used to detect ferricyanides by forming with 
them Turnbull’s blue; also tannic acid, with which, when per- 
fectly ‘free from ferric salt, it gives a white gelatinous precipitate, 
turning blue-black in air, while with gallic acid no precipitate is 
formed, but the colorless solution turns blue inair. Mol. W.= 
277.457. 

Tests. The pale bluish-green, monoclinic crystals must be free 
from yellow spots of ferric salt and form with water a perfectly 
clear pale greenish solution, whose reaction is neutral or but 
feebly acid. After acidulation with a drop of hydrochloric acid 
this solution must yield no precipitate with hydrogen sulphide. 
If, after being acidulated by boiling with sufficient nitric acid, the 
solution is precipitated by excess of ammonia water and the ferric 
hydrate filtered off, the filtrate, divided into three portions, must 
give no precipitate with ammonium sulphide (abs. of zinc), nor 
have a blue color or after acidulation by acetic acid give a red- 
brown precipitate with potassium ferrocyanide (abs. of copper) 
nor after evaporation and ignition leave any residue. 

PREPARATION. An excess of clean, fine iron wire is dissolved in 
pure, dilute sulphuric acid, the solution filtered, aciduiated slightly 
with sulphuric acid and concentrated. Thecrystals are drained on 
a funnel washed with a little acidulated water, dried and carefully 
preserved. The solution is only made when needed, with water 
previously boiled to expel oxygen. 

A very good article may be obtained from the residue of the sul- 
phuretted hydrogen apparatus, if pure ferrous sulphide and pure 
acid have been employed. 


FERROUS AMMONIUM SULPHATE, Fe S Os (N H,)2 S O4 + 6 He O. 


Uses. This salt serves for the same purposes as ferrous sulphate; 
being less liable to oxidation it is also used in volumetric analysis 
for adjusting the titre of potassium permanganate solution. Mol. 
W. = 891.363. 

Tests. This salt must, in addition to the same tests as ferrous 
sulphate, stand a quantitative comparison with pure iron, so as to 
show that it reduces an equivalent amount of potassium perman- 
ganate. 3.91363 gr. must require the same number of Ce. of per- 
manganate, as 0.55913 gr. of iron. 

PREPARATION. 277.457 gr. of pure crystals of ferrous sulphate 
and 131.866 gr. of pure ammonium sulphate are separately dis- 
solved in a minimum of water at 70° C., mixed, a few drops of sul- 
phuric acid added, and permitted to cool while constantly agitated, 
so as to form very small erystals. These are carefully dried and 
preserved. 








MW, 


WMARPSH'S TEST 


FOR ARSENIC 





41PP" APPARATUS 





FOR HH, tS, eto 


5) 
s 
= 
: 
y§ 
) 
= th 
XN 











. 
ty 
: 
X 
8 
~ 
: 





AhesltesS bus bnan, Bf 


FERROUS SULPHIDE—POTASSIUM OXALATE. 1% 


FERROUS SULPHIDE, Fe S. 


Users. For the preparation of hydrogen sulphide. 

Tests. For most purposes the commercial ferrous sulphide fur- 
nishes gas of sufficient purity, especially if care is taken to thor- 
oughly wash it. But as arsenic and phosphorous are rarely en- 
tirely absent, evenin the purer article furnished by the trade, an 
absolutely pure article must be made from pure iron and pure sul- 
phur for accurate work, especially in forensie cases. Van der 
Pfordten states that passing the gas over fusing potassing sulphide 
at 350° C. furnishes hydrogen sulphide free from arsenic, even 
though very crude ferrous sulphide be used. Arsenic may be de- 
tected by dissolving the finely powdered ferrous sulphide in nitro- 
muriatic acid, removing the excess of nitric acid by evaporation, 
and adding to the residue zine and hydrochloric acid in a test tube 
covered with a cap of filter paper, on which a drop of concen- 
trated silver nitrate solution willindicate the presence of arsenic 
by turning first yellow and, on moistening, black (@wutzett’s test). 

PREPARATION. Pure, fine iron wire, cut in pieces of suitable 
length, is heated to bright redness in a hessian crucible, piece3 of 
pure sulphur are then gradually added until the massis well-fused; 
any excess of sulphur volatilizes. The fused mass is poured ona 
clean place, so as to form thin plates, which are broken into pieces 
of suitable size. 

Ferrous sulphide remaining after having been immersed in the 
acid of the apparatus, although well washed, rapidly deteriorates 
by oxidation, unless it be covered by glycerin. (Kubel.) 


FERROUS POTASSIUM OXALATE, Fe Kz (Cz Ox)2 + 2 He O. 


Usss. This reagent has been introduced by Eder as a general 
reducent of metals from their salts. It reduces at ordinary tem- 
peratures platinic chloride, potassium-platinic chloride, silver ni- 
trate, chloride, bromide and iodide to the metallic state; from 
mercuric chloride it precipitates metallic mercury by heating; ferro- 
and ferri-cyanides of iron are converted into the yellow potassium 
ferrocyanide, etc. The reagent acts not only in alkaline and in 
neutral, but also in acid solutions. Mol. W. =845.447. 


PREPARATION. To concentrated solution of pure ferrous sul- 
phate a concentrated solution of pure potassium oxalate is added, 
with constant stirring, until the precipitate of ferrous oxalate at 
first formed is redissolved, forming a clear, deep-red solution. Or 
else dry ferrous oxalate is boiled with a 80% solution of potassium 
oxalate until no more is dissolved. The dry double salt is very 
unstable, it decomposes with water, and remains in solution only 
through excess of potassium oxalate. 


Isinglass, see Gelatin, p. 106. 


118 KRYOLITE.—LEAD. 


KAOLIN. 


This native silicate of aluminium is used occasionally as a flux 
in dry assaying; also in the state of powder as an inert addition to 
vegetable powders to prevent them from adhering together while 
being extracted by asolvent. Itshould be of a pure white color 
and yield nothing soluble to water_or to very dilute hydrochloric 
acid. | 

KRYOLITE, Ale Fe.6 Na F. 


Usses. This native mineral, consisting of aluminium and sodium 
fluoride, is used in the place of fluorspar for the preparation of 
hydrofluoric and hydro-fluo-silicic acid; also, in dry assays, as a 
flux for removing silicic acid. 

Only pure white, translucent pieces, free from foreign enclosures 
must be selected. 


LEAD AND ITS COMPOUNDS. 
LEAD, Pb. 


Usses. Metallic lead, either granulated or in foil (for cornets), is 
used in the docimastic assay of ores and alloys of silver, gold, 
platinum, etc. For this purpose it must be either absolutely pure 
or, if containing silver only, this percentage must be accurately 
known, so as to be deducted in the calculation. The lead, during 
the process of cupellation, becomes oxidized and then yieldsits 
oxygen again to the sulphur, arsenie or antimony combined with 
the metals and helps, together with the borax used at the same 
time, to form slag, while the rest of the fused lead dissolves the 
silver, gold, ete., and after oxidation leaves them behind as a “‘but- 
ton.’? Various amounts of test lead are used according to the 
quality of the ore oralloy. The weight in these operations is 
frequently expressed in assay-tons. The American assay-ton = 
29.166 grammes (450.26 grains troy), so that the number of milli- 
grammes of metal found in 1 assay-ton of ore corresponds to the 
number of troy ounces in 1 ton of 2,000 pounds avoirdupois. Pb = 
206.471. 

Tests. Pure lead has spec. gr. 11.37, and melts at 326°C. When 
perfectly pure melted lead shows a convex surface like mercury, a 
flat surface indicates impurities. For most purposes it is suffi- 
cient to test 1 assay-ton by cupellation, when it must leave either 
no residue or one of pure silver, which is weighed and noted for 
correction. When greater accuracy is required the test lead is dis- 
solved in pure, dilute nitric acid and must stand the following 
tests: After great dilution a few drops of hydrochloric acid must 


LEAD ACETATE. 119 


either give no precipitate or one which will dissolve readily in am- 
monia water, indicating silver. A portion of the nitrate solution 
is then precipitated with pure dilute sulphuric acid, the mixture is 
evaporated until all the nitric acid is expelled and vapors of sul- 
phuric acid begin torise The residue, still containing a small ex- 
cess of sulphuric acid, is mixed with dilute alcohol and filtered. 
From the filtrate the alcohol is evaporated and the silver (if any) 
precipitated by hydrochloric acid and filtered off. The clear fil- 
trate on evaporation and ignition must leave no residue; another 
portion must give no arsenic reaction; another should yield no pre- 
cipitate with hydrogen sulphide, nor, after addition of ammonia, 
with ammonium sulphide. 

PREPARATION. The purest lead from ‘‘Pattinson’’ process is 
sufficiently pure for most purposes, and is either rolled into sheet 
or foil or granulated by agitation while melted. For absolutely 
pure metal it must be reduced from a pure lead salt by electrolysis. 
Or the purest litharge obtainable is fused and, from time to time, 
some lamp black (or oil) is sprinkled upon the surface. This re- 
duces a small portion of the oxide to metal, which dissolves the 
silver and, by means of its greater specific gravity, sinks to the 
bottom; from thence it is removed and the operation repeated, 
Finally, the mair bulk of the litharge is reduced and is now free 
from silver. 


LEAD ACETATE, Pb (C2 Hs O2)2 + 3 Hz O. 


Uses. For the detection of hydrogen sulphide paper moistened 
with solution of lead acetate is often used, and shows its presence 
by the brown to black color of the lead sulphide formed. Also for 
the detection and precipitation of several acids, some of which 
are recognized by characteristic color or other properties, among 
them chromic, hydriodic, phosphoric, malic acid, ete. For the re- 
moval from urine of mucin, albumin, etc., by precipitation. For 
the precipitation of tannic acids and coloring materials, etc., from 
vegetable extracts. Also for the preparation of basic lead acetate 
and of pure lead. It is also used for the detection of glucose and 
lactose. When a solution of lead acetate and then ammonia 
water, drop by drop, are added to solutions of sugars, urine, etc., 
the white precipitate indicates the presence of glucose or lactose 
by assuming a red color after standing for some time (Rubner). 

It also serves to separate gallic from tannic acid, the lead salt of 
gallic acid being soluble, that of the tannic insoluble in acetic acid 
(Guyard). 

In very dry air or in the exsiccator it loses its water of crystal- 
lization and becomes epbydrouge ih (Ce Hg O2)2 = 824.207. 


120 LEAD SUBACETATE SOLUTION, 


Tests. Pure lead acetate crystallizes in transparent monoclinic 
tables, soluble without residue in 1.8 parts of pure water, at 15° 
C.,from which carbonic acid has been expelled by boiling. A 
slight residue of carbonate must dissolve in dilute acetie acid. In 
alcohol about an equal weight of lead acetate dissolves at 70°C. On 
cooling, Pb (Cz Hz O2)2 + 2 HzO precipitates, leaving less than 4% in 
solution. With litmus, but not with phenol-phthalein, lead ace- 
tate gives an alkaline reaction, Potassium ferrocyanide must pro- 
duce a pure white precipitate. After precipitation of the aqueous 
solution by hydrogen sulphide, and the expulsion of the excess of 
H2S by boiling, the filtrate must not form a precipitate with silver 
nitrate, nor with barium chloride, nor yield on evaporation a fixed 
residue. The watery solution, after precipitation with ammonium 
carbonate, must show no blue color. The U.S. P. preparation is 
sufficiently pure for nearly every purpose. 

PREPARATION. The test solution is made by dissolving one part 
of lead acetate in ten parts of pure water. 


LEAD SUBACETATE SOLUTION. 


Under this general designation a solution of several basic lead 
acetates, in various proportions, is known. That used in analysis — 
corresponds with the preparation of the Ph. Germ., and contains 
nearly equal proportions of triplumbic acetate, 2 Pb (C2 Hs O2)2 + 
Pb (O H)z, and diplumbie acetate, Pb (Ce Hg O2)2 + Pb (OH), 
while that made according to the U. S. P. contains principally 
the latter salt, but may in most cases be substituted for the other. 

Uses. ,For the separation of gums, tannic acids, coloring mate- 
rials, etc., from vegetable extracts, syrups, sugars, beer, urine, etc.., 
previous to examination by the polariscope or by reagents for 
sugars, alkaloids and other substances not precipitated by the 
lead salt. Also for the determination of lactic acid (Palm). Also 
for the precipitation of albuminoids, to separate them from pep- 
tones, etc.,in which case the lead solution is mixed with alcohol. 
(Palm). 

Tests. It should conform to the same tests for freedom from 
impurities as the neutral acetate, when wanted quite pure. For 
most purposes the pharmacepial preparations are sufficiently pure. 
Spec. gr. 1.228 to 1.24. 

PREPARATION. Into a very strong and capacious flask 300 gr. of 
pure lead acetate, 100 gr. lead monoxide (pure litharge) and 1 litre 
of water are placed and secured to the flywheel of some moving 
machinery, so as to keep the mixture thoroughly agitated for from 
10 to 12 hours; or heat is applied on a water bath, with occasional 


LEAD CHLORIDE—CAROMATE. 121 


shaking, for a less time. The mixture is then filtered and care- 
fully preserved from contact with carbonic acid. 


LEAD CARBONATE, Pb C Os, and the basic white lead, Pb (O 
H)z. 2 Pb C Os, are used as flux instead of litharge or other lead 
compounds. Also for the removal of tannic acids from solutions 
(Jackson). For either purpose an unadulterated article of commer- 
cial white lead is sufficiently pure, if it is completely soluble in so- 
lution of sodium hydrate. 


LEAD CHLORIDE, Pb Ch, 


Uses. A saturated solution of lead chloride either in water or 
in solution of pure sodium chloride, in which it is more soluble, 
produces in solutions of the hydrochlorides of most alkaloids 
colorless, crystalline precipitates of double salts. Quinine and bru- 
cine in crystalline powder; morphine, codeine and cinchonine in 
needles; strychnine in felted fibres, etc. From these the alkaloids 
may be separated by Hz S or by sulphuric acid (Palm). Also, in 
alcoholic solution, for the precipitation of albuminoids, even in the 
smallest traces (Palm). Pb Cle = 278.268. 

Tests. Lead chloride forms long, colorless, rhombic prisms 
soluble at 15°C. in 105 parts of pure water (requiring up to 135 
parts, if a little hydrochloric acid is present); at 100°C. in 23 parts 
of water. Absence of other metals is shown by the same tests as 
for metallic lead or lead acetate. 

PREPARATION. A saturated solution of pure lead acetate in 
water is precipitated by avery slight excess of pure hydrochloric 
acid. The precipitate after washing is dissolved in boiling water 
and the crystals preserved, which separate on cooling. 


LEAD CHROMATE, Pb Cr 04, 


Uses. Fused lead chromate in fine powder is used for the oxi- 
dation of hydrogen and carbon in the ultimate analysis of or- 
ganic compounds. It is thereby reduced to chromic oxide and a 
basic chromate. It is preferred before cupric oxide in the case of 
some non-volatile substances, which are more difficult to oxidize, 
and is sometimes used either jointly with cupric oxide or mixed 
with potassium dichromate. 

Tests. Lead chromate after fusion and powdering has a brown. 
ish-yellow color. Its most troublesome impurity is organic matter, 
accidently present through careless preservation. On heating to 
fusion it must yield neither carbon dioxide nor water, at a higher 
heat it must give off pure oxygen. 

PREPARATION. A clear solution of 21 parts of crystallized lead 
acetate is precipitated by a solution of 16 parts of potassium dichro- 


122 LEAD NITRATE—OXIDES. 


mate. The precipitate after washing and drying is fused in a hes- 
sian crucible, cast into thin plates and powdered while yet warm. 
It must be carefully preserved from dust and moisture. After use 
it may be regenerated by thorough washing, moistening with nitric 
acid and fusing. A current of oxygen may serve instead of nitric 
acid. 


LEAD NITRATE, Pb(N Os)o. 


Usrs. In some cases it is used as a substitute for lead acetate, 
in quantitative analysis it serves to oxidize arsenous into arsenic 
acid. 

Tests. Lead nitrate forms regular octohedral crystals, soluble 
in 2 parts of pure water. The tests for absence of cther metals 
are the same as for other lead salts. 

PREPARATION. Pure lead monoxide is dissolved in a slight ex- 
cess of nitric acid and recrystallized from hot water. 


LEAD OXIDES. 


LEAD MONOXIDE, Pb O, Litharge. 

Uses. Pure monoxide is used in quantitative analysis for the 
separation of phosphoric and arsenic acid, and, in conjunction 
with lead nitrate for that of arsenous acid. In assaying litharge, 
which needs not to be absolutely pure, is used for removing silica 
and as an oxidizing flux. It also serves to prepare pure metallic 
lead, ete. 

Tests. Other metals are to be detected by the same tests as for 
other lead salts. The following generally suffices: Metallic lead ig 
_ found as a residue after solution in acetic acid; no effervescence 

a must occur during this solution, showing ee of carbonate. 

“Te filtered solution is precipitated by dilute sulphurie acid in 
slight excess, and the precipitate filtered off. The filtrate, after 
addition of ammonia, must neither show a blue color (copper), 
nor a precipitate (iron, aluminium). 

PREPARATION. On the larger scale litharge is obtained as a bye- 
product of the cupellation of argentiferous lead. Pure monoxide 
for the determination of arsenic is made by precipitating a solution 
of pure lead acetate or nitrate by ammonium carbonate, washing 
the precipitated carbonate and expelling C Oe by ignition. It 
should be carefuly preserved, as it = acts C Oe from the atmos- 
phere. 






RED LEAD, Pbs O4, is used as an oxidizing agent; to prepare 
chlorine from hydrochloric acid; to detect strychnine, and asa 
flux for oxidizing sulphides, etc., and for removing silicic acid by 
converting it into a fusible slag. 








MAGNESIUM. 123 


LEAD DIOXIDE, Pb Ox. 

Uses. For the separation of bromine from chlorine, especially 
in water analysis. The mixed haloid salts of the residue, from 
which iodine has been removed by palladious chloride or nitrate, 
are introduced into a retort, together with lead dioxide and acetic 
acid. Bromine is liberated and distils over, while the chlorides 
are not decomposed (Wortmann). 

Tests. The brown-purple powder must not yield anything sol- 
uble to nitric acid. 


PREPARATION. A pure article of red lead is digested with an 
excess of nitric acid, and the process repeated as long as the nitric 
acid extracts anything. Itis then thoroughly washed and dried. 


LEAD HYDROXIDE or HYDRATE, Pb (O H):. 

Uses. Freshly precipitated hydrate dissolves to a small amount 
in pure water. This solution precipitates albumin, forming one of 
the most delicate reagents (Palm). The solid hydrate is some- 
times used for the precipitation of tannic acid. 


PREPARATION. Solution of pure lead acetate or nitrate is pre- 
cipitated by an insufficient amount of potassium or ammonium 
hydrate, the precipitate thoroughly washed with boiled water and 
preserved free from contact with carbonic acid gas. 


Litmus, see Color Reagents, page 84. 


MAGNESIUM AND ITS COMPOUNDS. 
MAGNESIUM, Mg. 


Uses. As it is more easy to obtain metallic magnesium free 
from arsenic than zinc, the metal is sometimes substituted for zine 
to generate pure hydrogen with sulphuric or hydrochloric acid; _ 
from alkaline hydrates it does not liberate hydrogen; hence, it 
may be used to advantage in Marsh’s or Gutzeit’s arsenic test, but 
not in Fleitmann’s, unless it has been platinized. When a few 
drops of platinic chloride solution are dropped upon magnesium 
it becomes coated with a thin film of platinum, and will now de- 
compose even pure water. (The same process of platinizing is 
also applied to zinc and cadmium to render them more soluble in 
acids.) It may then also be used to great advantage for many re- 
ducing operations, e. g., to convert nitro-benzol into aniline (Balle). 
Magnesium also serves in the wet assay to precipitate lead (Roess- 
ler). As burning magnesium is very rich in the violet and ultra- 
violet rays, it is sometimes used as a source of light to detect fluor- 
escent substances, e. g., quinine in urine. Mg. = 23.959. 


124 MAGNESIUM CARBONATE, 


Tests When asmall piece of pure magnesium is treated with 
pure dilute hydrochloric acid ina test tube covered with a cap of 
filter paper, upon which a drop of concentrated silver nitrate solu- 
tion is placed, the color of the silver spot must not change to yellow 
or brown for an hour (absence of arsenic by Gutzeit’s test). The so- 
lution in the tube, subdivided into several parts, must yield no 
precipitate with H2S, nor, after neutralization by ammonia, with 
ammonium sulphide or carbonate. After precipitation by ammo- 
nium phosphate the filtrate must leave no residue after evapora- 
tion and ignition. The magnesium of commerce is generally pure 
from all other metals, except a trace of sodium, which is rarely 
objectionable, or some superficially adhering iron (from rusty rol- 
lers), which is easily removed by scraping. 

PREPARATION. Seven parts of pure sodium chloride are fused 
together with 9 parts of potassium chloride, and, after cooling, are 
reduced to fine powder and intimately mixed with 96 parts of an- 
hydrous magnesium chloride and 16 parts of fluorspar. A crucible, 
provided with cover, is heated in a furnace, and, as soon as it at- 
tains a bright red heat, 16 parts of metallic sodium are rapidly cut 
into small pieces, incorporated with the above mixture and put 
without delay into the crucible, which is then closely covered. 
A peculiar noise accompanies the reaction and, as soon as thisis 
complete, the crucible is removed from the furnace. After the 
red glow has disappeared, but before the mass has solid- 
ified, the lid is removed and the small globules of mag- 
nesium are, by means of a clay pipe stem, collected to a 
single mass, the lid is then replaced and, after cooling, the 
metallic magnesium is freed from adhering slag by washing with 
water, and, if needed, even with a little dilute hydrochloric acid 
(Fittig). The metal has asilvery lustre and spec. grav. 1.75. 


MAGNESIUM CARBONATE. MgC Os: + 3 H20. 


Usrs. This salt, as well as its basic compounds of various com- 
position (Mg C O3. Mg (O H)2 + 3 He O and 3 Mg C Os -+Meg (O H)e 
+. 4 H2 O) is occasionally used in iron analysis and for saturation 
of acids instead of the oxide and hydrate; also for the preparation 
of other magnesium compounds. Mg C Os = 83.818. 

Tests. Itisalight, white, flocculent substance of which only 
traces are soluble in water. In dilute acetic acid it must dissolve 
without residue. The solution, after expelling C O2, must not be 
rendered turbid by Hz S nor by ammonium sulphide, carbonate or 
oxalate after addition of-a sufficient amount of ammonium 
chloride and hydrate. It must be entirely free from sulphate or 


MAGNESIUM CHLORIDE. 125 


chloride; hence, no turbidity must be produced by silver or 
barium nitrate. 

PREPARATION. Cold saturated solutions of magnesium sulphate 
(4 vol.) and sodium carbonate (10 vol.) are mixed. After standing 
for a day or two, the precipitate is collected on a filter and washed 
with distilled water until the filtrate is no longer rendered turbid by 
barium chloride or silver nitrate. The product then consists of 
Me CO3+3H:;O. If made at higher temperature it loses C Oz and 
contains various proportions of Mg (O H)a. 


MAGNESIUM CHLORIDE, Mg Clo. 


Usrs. The anhydrous salt is used for the preparation of the 
pure metal. The hydrated, Mg Cle-+ 6H20O, serves instead of 
magnesium sulphate for the precipitation of phosphoric acid, 
where the introduction of a sulphate is objectionable. Mg Clk = 
94.699; Mg Cle + 6 He O = 202.459. 


Tests. It must be free from all other bases and from sulphate 
and phosphate. The absence ot other bases is shown by the same 
tests as described for sulphate or carbonate. Its solution must not 
give a precipitate for several hours after being mixed with am- 
monium chloride and hydrate, nor with barium chloride. The erys- 
tals must dissolve without residue in 5 parts of concentrated 
alcohol. With sodium hydrate it must not yield ammonia vapor. 


PREPARATION. The hydrate may be made by adding a slight 
excess of magnesium oxide to hydrochloric acid, shaking up fre- 
quently, filtering and evaporating, but not to dryness. The crys- 
tals obtained must be protected from moisture. The anhydrous 
salt is made by adding to the above solution twice as much ammo- 
‘nium chloride as there had been used of magnesium oxide, eva- 
porating to dryness and then igniting at as low a temperature as 
possible to expel all the ammonium chloride. The salt must be 
carefully protected from moisture. 


Magnesia mixture (with chloride) for precipitating phosphoric 
acid is made by dissolving 1 part of Mg Cle + 6 He O and 2.5 parts 
of ammonium chloride in 10 parts of pure water and adding 5 
parts of ammonia water, and filtering after standing for several 
days. 

Magnesium hydrate, Mg (O H)s, is occasionally used in the search 
for alkaloids for the removal of ammonia, amines and volatile 
ptomaines (Tamba). For this purpose it is precipitated from mag- 
nesium sulphate by an alkaline hydrate and used after thorough 
washing. 


126 MAGNESIUM OXIDE—SULPHATE. 


MAGNESIUM OXIDE, Mg O. 


Usrs. The oxide, also known as calcined magnesia, is occasion- 
ally used in the analysis of iron, for the removal of phosphoric and 
arsenic acid, etc., and for preparing other magnesium salts. Mg 
C= 9 O10: 

Tests. In dilute acetic acid it must dissolve without efferves- 
cing or leaving any residue. This solution must yield no precipi- 
tate with H2S; after addition of ammonium chloride and hydrate 
in slight excess no precipitate must fall (abs. of phosphoric acid, 
aluminium, ete.); nor mustfurther addition of ammonium sulphide 
or oxalate produce either precipitate or color. After precipitating 
from the acetic solution all the magnesia by addition of ammonium 
hydrate and phosphate, the filtrate must, after ignition, leave no 
residue. The solution innitric acid must yield no precivitate with 
the nitrate of barium or silver. It requires about 55000 parts of 
water for solution. 

PREPARATION. Magnesium carbonate is heated to a red heat, in 
a suitable crucible, until all carbon dioxide has been expelled. It 
must be carefully protected from moisture and air. 


MAGNESIUM SULPHATE, Mg S 0:+ 7 H2 O. 


Usss. For the detection and quantitative determination of phos- 
phorie and arsenic acids, which are precipitated as double salts of 
ammonium and magnesium. For this purpose a solution of mag- 
nesium sulphate, ammonium chloride and hydrate is usually em- 
ployed under the name of magnesia mixture; also for the precipi- 
tation of globulin and its separation from albumin (Hammarsten). 
Also for testing ammonium sulphide for presence of free ammonia 
or carbonate (see page 39). Mg.S O4-+ 7 He O = 245.408. 

Tests. Pure magnesium’ sulphate forms transparent, rhombic 
prisms, soluble in 0.8 parts of cool and in 0.15 parts of boiling 
water, insolubleinalcohol. Its reaction is neutral. Its solution in 
water, after acidulation with acetic acid, must not be precipitated 
by He 8; after addition of ammonium chloride and hydrate in slight 
excess no precipitate must fall, nor must the further addition of 
ammonium sulphide or oxalate produce either color or precipitate. 
even after some length of time. Silver nitrate must produce no pre~ 
cipitate. The flame must not show the sodium reaction. After 
precipitating the watery solution of magnesium sulphate by am- 
monium phosphate and hydrate the filtrate must leave no residue on 
ignition. 

PREPARATION. Epsom salt, selected as pure as obtainable, is 
dissolved in boiling water, digested for some time with a small 


MANGANESE DIOXIDE—MANGANOUS SULPHATR. 127 


amount of magnesium oxide, filtered, crystallized in small crys- 
tals and recrystallized, if necessary. 

Magnesia mixture is made by dissolving 1 part of magnesium 
sulphate and 2 parts of ammonium chloride in 8 parts of water, 
adding 4 parts of ammonia water and filtering after the mixture 
has stood for several days ina closed vessel. 

Magnesium sulphide, Mg S and hydrosulphide, Mg (S H)s are 
sometimes used to prepare sulphuretted hydrogen free from ar- 
senic, by heating them while moist (Divers and Shimidzu). The 
sulphide is prepared by heating to redness an intimate mixture of 
magnesium sulphate and lampblack. The hydrosulphide is made 
by mixing an alkaline sulphide with magnesium sulphate. The 
mixture on moistening and heating gently gives off He S in a regu- 
lar current (Gerhard). 


MANGANESE COMPOUNDS. 
MANGANESE DIOXIDE, Min O2. 


Usrs. For the preparation of chlorine, bromine, iodine, oxygen, 
manganates and permanganates, etc.; also for absorbing gases 
(hydrogen sulphide, sulphur dioxide). Mn O, = 85.826 

Tests. The native mineral varies considerably in composition. 
Some varieties have a large percentage of Mn Os, and but a small 
amount of lower oxides of manganese and iron, while others are 
of low grade, containing carbonates, silicates, etc. The dark gray 
erystals of pyrolusite, containing 90% or more of Mn Oz, should be 
selected in preference to the soft, black varieties. Freedom from 
carbonates should be tested for by acetic acid, which should not 
produce effervescence. Its percentage of available oxygen may 
be readily ascertained by Fresenius and Will’s method, in their 
two-flask apparatus, by converting oxalic acid by means of man- 
ganese dioxide and sulphuric acid into C Og, and ascertaining its 
amount by loss of weight (Mn O2-+ He S O4 + He Ce Os = Mn § Og 
+ 2 He O + 2 C Or). 


MANGANOUS SULPHATE, Mn S 01 + 7 H2 O. 


Uses. For the titration of boracie acid, which it precipitates as 
manganous borate, Mn Be Ou, insoluble in alcohol (Hdg. F’. Smith). 
Also for the detection of chromates in presence of dichromates by 
the brownish-black precipitate of manganese chromate (Donath), 
Mn 8 O14 = 149.78. 


Tests. Manganous sulphate at different temperatures crystal- 
lizes with different amounts of water. Below 6° C. Mn S O44 7H2O 


128 MENTHOL—MERCURY OR QUICKSILVER. 


forms in pink colored, monoclinic prisms; above 7° C. and be- 
low 19° C. triclinic prisms of red color, containing 5 He O; between 
20° C. and 80°C. monoclinic prisms with 4 He O; above that tem- 
perature still less water, in colorless crystalline powder, of but 
slight solubility. It must not give the iron reaction with potassium 
ferrocyanide. 


PREPARATION. On a large scale it is obtained generally as a 
bye-product of other manufactures. It may be made by heating in 
acrucible the purest dioxide with aslight excess of sulphuric acid, 
until all the free acid evaporates; then raising the heat for a short 
time to redness so as to decompose the iron sulphate. The residue 
is leached out with water and recrystallized for purification. 

Manganates and permanganaics are described under their resp. 
bases, see potassium salts, etc. 


MENTHOL, Cio Ha O. 


Usrs. To detect glucose in urine, etc. With carbohydrates and 
concentrated sulphuric acid it produces a red color. Hence, a few 
drops of 215% solution of menthol in alcohol are added to the li- 
quid to be tested and conc. H, S OQ, poured into it, so as to form a 
layer beneath. If glucose ora glucoside or carbohydrate is present 
the zone of contact assumes a cherry-red color (Molisch). 

Tests. The colorless or white crystals melt at 42° C. and boil at 
212°C. At 100° C. they volatilize, and, if pure, leave no residue. 
When heated with a mixture of 2 parts of concentrated sulphuric 
acid and 1 part of water the melted menthol becomes at first 
brownish-red and finally deep blue, while the acid assumes a red 
brown color. The commercial article sold as ‘‘pip-menthol’’ is 
sufficiently pure. 

PREPARATION. Pure oil of peppermint is solidified by a freezing 
mixture and reduced to —22° C. The solid is placed upon a fun- 
nel and slowly permitted to assume the surrounding temperature. 
A portion becomes liquid again and drains away, while the crystals 
remain on the funnel. 


MERCURY AND ITS COMPOUNDS. 
MERCURY or QUICKSILVER, Hg. 


Usss. For the preparation of its various salts. For amalgama- 
tion of copper, tin, sodium, zine, ete. For filling tubes, etc., ina 
number of experiments, especially in gas analysis, where a heavy 
liquid is required to confine gases or liquids and keep them sepa- 
rated from each other. Hg = 199.712. 


MERCURIC CHLORIDE. 129 


Tests. A small drop, heated in a porcelain capsule, must vola- 
tilize without residue. When boiled for 1 minute with a concen- 
trated aqueous solution of pure sodium hyposulphite it must not 
become tarnished. When rolled over white paper it must leave no 
trail. A solution of ferric chloride, shaken for some minutes with 
mercury, must not indicate any reduction by giving with potassium 
ferricyanide a blue precipitate. It must dissolve without residue in 
dilute nitric acid and, after precipitation by Hz S, the filtrate must, 
on evaporation, leave no fixed residue. Very dilute nitric acid is 
digested at ordinary temperature with an excess of mercury until 
saturated. Some of the solution is then precipitated by a slight 
excess of hydrochloric acid and rapidly filtered. The precipitate 
must not yield any lead chloride to boiling water, nor silver chlor- 
ide toammonia. The filtrate must give no precipitate with hydro- 
gen sulphide. 


PREPARATION. Pure mercury is best made from the crude com- 
mercial by distillation, an apparatus being employed for 
distillation under reduced pressure. For most purposes of 
gas analysis mercury may be purified sufficiently by digesting 
for several days with dilute nitric acid, washing, drying by blotting” 
paper and then pressing through chamois leather. 


MERCURIC CHLORIDE, Hg Cl,. 


Usrs. Mercuric chloride, also called corrosive sublimate, is used 
for the detection and quantitative determination of small traces 
of arsenic, which are liberated as arsenetted hydrogen and passing 
through a solution of mercuric chloride deposit all of their arsenic 
as a yellow or brown compound with mercury (Mayeng¢on and Ber- 
geret). Also for the detection and volumetric determination of 
iodides, producing with them scarlet HgI,. It yields up its chlorine 
either partly or entirely to reducents (Ag, Sb, As, Bi, Sn, As, Fe), and 
is thereby converted into mercurous chloride and finally into metallic 
mercury. Hence, it serves to detect tin, which it converts from stan- 
nous to stannic chloride; also formic acid, etc., etc. It precipitates 
some of the alkaloids (strychnine, colchicine, etc.); also gelatine 
and albuminoids as mercuri-albuminate. The latter reaction is 
most sensitive when the double salt Hg Cl, + 2 Na Cl, mixed with 
citric acid, is employed (Stwetz). It is also used to detect ammonia 
and ammonium carbonate by forming with them a white precipi- 
tate of mercur-ammonium chloride. For other ammonia salts 
the oxychloride (Bohlig’s reagent) is used. It also serves to distin- 
guish alkaline carbonates, which produce a red-brown precipitate 
of basic mercuric carbonate, from di-carbonates, which give no 


130 MERCURIC CHLORIDE, 


precipitate. Itis also used as a microchemical reagent to coagu- 
late and harden certain tissues and render them more visible under 
the microscope. Also to prepare a number of mercurial com- 
pounds, mercuric iodide, Nessler’s test, Bohlig’s and Mayer’s solu- 
tions, etc. Hg Cl, = 970.452. 


Tests. Sublimed mercuric chloride forms transparent crystal- 
line crusts. When obtained from solution it forms rhombic crys- 
tals with acute terminals. It dissolves at 15° C. in 16 parts of water, 
in 3 parts of alcohol, of spec. grav. 0.820, or in 4 parts of ether; also 
in 2 parts of boiling water, or 1.2 parts of boiling alcohol. The so- 
lution in water reacts acid, but becomes neutral on addition of Na 
Cl. In the above solvents it must dissolve without residue. With 
Fleitmann’s, or similar tests, it must not give any arsenic reaction. 
After precipitation of its aqueous solution by H,S no residue 
should remain by evaporating the filtrate, nor should the precipi- 
tate yield anything soluble to ammonia. 

Commercial corrosive sublimate often contains a small amount 
of calomel, while otherwise pure. Such an article may be used 
for all solutions; but for decinormal volumetric solution the titre 
must be adjusted, or pure, recrystallized mercuric chloride taken. 


PREPARATION. On the large scale the salt is made by sublima- 
tion of mercuric sulphate mixed with sodium chloride, and this 
process may be imitated on the small scale with pure salts. The 
commercial product may be purified by recrystallization from 
boiling water, or from alcohol, if it does not completely dissolve 
in the latter. The test solution contains one part of mercuric 
chloride in 20 parts of water. 

Deci-normal solution contains 18.52 grammes of mercuric chlo- 
ride in 1 litre, the solvent consisting of 4 parts of water and 1 part 
of alcohol. It is used for the titration of K I; as long as more than 
2K I are in solution for each Hg Cle added, the red precipitate of 
Hg Ie redissolves, forming Hg Iz. 2 K I; but as soon as the Hg Cle 
exceeds this proportion, by even a single drop, the red precipitate 
remains undissolved and indicates the end of the reaction: 4 KI + 
Hg Ch =2KCl+ Hg ki.2K 1. 


A solution of mercuric oxychloride is somennnied employed as Boh. 
lig’s reagent for the detection of ammonium salts. Itis made by add. 
ing to a solution of 1 part of Hg Clein 30 parts of water, drop by 
drop, with constant agitation, a solution of 1 part of potassium 
carbonate: in fifty parts of water, until the mixture ceases to red- 
den litmus paper. The brown-red precipitate is filtered off; the 
clear filtrate indicates the presence of ammonium salts by a 
white precipitate, 


MERCURIC CYANIDE—IODIDE—POTASSIUM IODIDE. 131 


MERCURIC CYANIDE, Hg (C N)a 


Uses. For the volumetric determination of glucose, which in 
alkaline solution reduces it to metallic mercury (Knapp). 

Tests. The salt crystallizes in colorless quadratic prisms, 
soluble in 12.8 parts of water at 15° C., in three 
parts at 100° C.; somewhat less soluble in alcohol. With 
potassium cyanide it forms a soluble double salt, Hg (C N)2. 
2K CN. Its watery solution should not turn turmeric paper brown. 
With a very dilute solution of potassium iodide, added drop by 
drop, it should not yield a red precipitate of Hg Ie; after acidula- 
tion with nitric acid its solution should not give a precipitate with 
Silver nitrate. At an elevated temperature it should separate into 
gaseous cyanogen, brown solid paracyanogen and metallic mer- 
cury, and should finally at 860° C. volatilize without residue. 

PREPARATION. Mercuric oxide is dissolved in a slight excess of 
hydrocyanic acid, concentrated by evaporation at a low tempera- 
ture in the dark, and the crystals carefully protected from light. 

Knapp’s volumetric solution contains 10 grammes mercuric cyan. 
ide and 12.5 gr. sodium hydrate, dissolved in water to make 1 litre, 
One decigramme of glucose reduces 40 Ce. of the solution. Am- 
monium sulphide is used as indicator by the method of “spotting.”’ 


MERCURIC IODIDE, Hg Iz and MERCURIC POTASSIUM IODIDE, 
Hgle.2K I. 


Usrs. Mercuric iodide is used to make a permanent iodized 
starch solution, to serve as indicator, by triturating 0.1 gr. Hg Is 
with 5 gr. of starch and some water, and, after solution, diluting 
' tollitre (Gastine). The double salt, called also potassium iodo- 
hydrargyrate, in neutral alkaline and acid solution, finds many ap- 

plications in analysis. Neutral, as Mayer’s solution, it serves for 
volumetric determination of alkaloids. Also for indicating the 
completion of the fermentation process of beer, as young beer 
gives only aslight turbidity, while old, ripened beer gives a copious 
precipitate with the reagent (Johanson). In alkaline solution it 
serves either as Sachse’s solution for volumetric determination of 
glucose or as Nessler’s test for detection and colorimetric determi- 
nation of ammonia, especially in drinking water. In acid solution 
it is used as Geissler’s test for detection of minute quantities of al- 
bumin and in milk analysis for the precipitation of all albuminoids 
(casein, etc.), preparatory to determining the lactose by polariza- 
tion. Hg Is= 452.826; Hg Ie . 2 K I = 783.978. 

Tests. Mercuric iodide forms a scarlet powder or quadratic 
crystals. It is insoluble in water, soluble in alcohol, acetic acid 


132 MERCURIC IODIDE—POTASSIUM IODIDE, 


and aqueous solutions of mercurie chloride or potassium iodide, 
forming with them colorless solutions. It should completely vola- 
tilize and give the other tests of purity from foreign metals, as de- 
scribed under mercuric chloride. In most cases itis used as pre- 
pared by potassium iodide and mercuric chloride, without sepa- 
rating the potassium chloride formed. 

PREPARATION. Solutions of 10 parts of mercuric chloride and 
of 12.25 parts of potassium iodide are mixed, the precipitate col- 
lected on a filter, washed and dried. 


MAYER’S SOLUTION is made of decinormal strength, and 
contains 13.546 gr. mercuric chloride and 49.8 gr. potassium iodide 
in 1 litre. It precipitates most alkaloids, forming with them gene- 
rally crystalline compounds either of the formula Alk lk . 
Hg Is, as aconitine, nepaline, atropine, hyoscyamine, coniine, nico. 
tine, emetine, colchicine, ete., or of the formula Alk 1. HI. Hg 
Tz, as strychnine, brucine, morphine, narcotine, quinine, cincho- 
nine, etc., etc. 

Occasionally, a solution of one-half the strength is employed 
(Lyons). 


SACHSE’S SOLUTION contains in 1 litre 18 gr. Hg Ie, 25 gr. 
K ITand 50 gr. K OH, dissolved in water. Of this solution 40 Ce. 
are placed in a porcelain capsule, and the glucose solution added 
from a burette as in Fehling’s process. It requires 0.1501 gr. of 
dextro-glucose to reduce the 40 Ce. of solution to metallic mercury. 
An alkaline solution of stannous chloride serves as indicator to 
show the complete reduction of Hg by spotting. 


NESSLER’S SOLUTION for the detection and colorimetric de- 
termination of ammonia is made by mixing 50 gr. of K I, dissolved 
in 50 Ce. of hot water, with a hot solution of 25 gr. of Hg Cle in 100 
Ce. of hot water, adding to the turbid red mixture a solution of 160 
gr. of K O H (or 120 gr. of Na O H) in 400 Ce. of water, and filling 
up, after cooling, with (distilled) water to1 litre. The solution, 
after standing, deposits its surplus of Hg Iz, and may be decanted, 
but it is essential that a full saturation with Hg I, should be made, 
lest an excess of K I should redissolve the precipitate made by am- 
monia. Some direct 66.4 gr. of K I and 27.1 gr. of Hg Cl., so as to 
niake the solution one-fifth normal. Of this solution 1 Ce. eachis 
added in Nessler cylinders, having the 50 Ce. mark at equal height 
from bottom, to the specimen of water to be tested and to 4 speci- 
mens containing various amounts of standard ammonia solution. 
A reddish-yellow color indicates the presence of ammonia, and by 
comparison of the depth of color the quantity is estimated. 





MERCURIC NITRATE. 133 


GEISSLER’S SOLUTION, for detecting and removing albumin- 
oids, is made by dissolving 13.5 gr. Hg Cl, and 338.2 gr. K I in 20 
Ce. acetic acid of spec. gr. 1.048 and 64 Cc. of water, and aiding so- 
lution by gentle heat. In this strength it serves to precipitate 
albuminoids from milk, of which various quantities are taken, ac- 
cording to its specific gravity, and obtaining a solution ready for 
determining lactose by the polariseope. For mere qualitative de- 
tection of albumen a much weaker solution is used, made by add- 
ing to the above amount 400 Cc. of water instead of 64 Cc. 


MERCURIC NITRATE, Hg (N 0s),. 


Uses. In solution containing nitrous acid and but slight excess 
of nitric acid it serves to detect albuminoids, tannin, guaiacol, eu- 
genol, vanillin, etc., by producing a red colored precipitate (Mil- 
lon’s reagent). Also for the precipitation of the albuminoids of milk _ 
preparatory to estimating lactose by polarization. For the volu- 
metric determination of urea by Liebig’s method. Hg (N Os), = 
323.514. 


Tests. Mercuric nitrate must not give a white precipitate with 
hydrochloric acid (abs. of mercurous salt, etc.). By heat it is first 
converted into red oxide and then completely volatilized. Tests 
for admixture of other metals are the same as for mercuric chlor- 
ide. The salt may crystallize with various amounts of water. So- 
lution of the perfectly neutral salt in water gradually decomposes 
it, and protracted boiling precipitates mercuric oxide. 


PREPARATION. By dissolving pure mercury in a slight excess of 
hot conc. nitric acid and crystallizing. 

Liebig’s volumetric solution is made by dissolving 77.2 grammes 
of pure mercuric oxide in a slight excess of nitric acid and diluting 
to 1 litre. Each 1 Ce. corresponds to 10 Mgr. urea. In adding the 
solution to urine care must be taken to neutralize the liberated 
acid by repeated additions of sodium carbonate (calcium carbonate, 
Pflueger). A white precipitate of a compound containing 1 mole- 
cule of urea and 2 mol. of mercuric oxide, C O (N H,), .2 Hg O, 
falls as long as urea is present. As soon as it is all removed, the 
mercuric solution is converted into a reddish precipitate by the 
sodium carbonate used as indicator. Sometimes the chlorides are 
first removed by silver nitrate, an excess of which does not inter- 
fere (Rautenberg). 

Millon’s reagent is made by dissolving 1 part of mercury in 1 part 
of nitric acid, of spec. gr. 1.42(up to 1.52), and, after complete solu- 
tion by the aid of heat, adding an equal volume of water. It should 
contain N, Os, but no great excess of nitric acid. When, by long 


134 MERCUROUS NITRATE—MERCURIC OXIDE. 


preservation, nitrous acid has become deficient, the reagent is no 
longer sensitive, but may be restored by adding a little K N Og. 
For removing albuminoids from milk a solution is used containing 
double the amount of nitric acid as Millon’s solution (Hoffmann’s 
reagent). 

MERCUROUS NITRATE, Hgp (N Os)2 + He O. 


 Usss. For detecting some acids, especially those of the chlorine 
group, by characteristic precipitates. For separating phosphoric 
acid from bases (H. Rose). Also for oxidation of some reducents 
(formic acid, etc.), which separate from it metallic quicksilver. 
Also for detecting brucine, which, with mercurous nitrate free 
from excess of acid, gives a red color (flueckiger). 

Tests. The salt forms transparent, monoclinic crystals, which, 
in water acidulated with nitric acid, dissolve without change, but 
are soon decomposed in solution in pure water, a yellow basic 
salt, Hge(N Os)2H 20-+ He O, being deposited. Other basic salts form 
when metallic mercury is kept in contact with the neutral solution, 
but the formation of mercuric salt is thereby prevented. Light de- 
composes the salt. Addition of aslight excess of dilute hydro- 
chloric acid should completely precipitate the mercury as calomel 
and leave in the filtrate nosubstance capable of being blackened 
by Hz S or of leaving a fixed residue on heating. Other tests are 
the same as for mercuric chloride. 

PREPARATION. Equal weights of pure quicksilver and nitric 
acid of spec. gr. 1.2 (made by mixing 7 parts of water with 6 parts 
of pure nitric acid of spec. grav. 1.42) are placed for 24 hours in a 
porcelain capsule in a cool, dark room. The crystals are then 
separated, carefully drained and preserved in opaque bottles. For 
use they are dissolved in 10 parts of water containing about 
5% of nitric acid, and the solution preserved in an opaque bottle 
containing a small amount of metallic mercury. When contain- 
ing some free nitrous acid the solution issometimes called Plugge’s 
reagent. 


MERCURIC OXIDE, Hg O. 


UssEs. Precipitated mercuric oxide in fine powder is used for 
the separation of magnesium from the alkalies, by digesting their 
chlorides with it. Alsoin the volumetric determination of cobalt 
by Winkler’s method for removing iron, manganese, etc. Also in 
the determination of nitrogen in organic bodies, according to 
Kjeldahl’s method, as an addition to shorten the time of digestion 
with sulphuric acid; the mercury being subsequently removed by 
Hz28, Also for separating uranium chloride from the chlorides of 


(ie 


METHYL IODIDE—METHYLENE IODIDE. 135 


other bases (Alibegoff). Also for the preparation of mercuric salts. 
Tests. It must volatilize without residue. The oxide prepared 
by precipitation in the state of a tine yellow powder is preferable 
to the red crystals obtained by the dry methods. 
PREPARATION. To a hot, dilute solution of pure sodium hydrate, 


which must be kept in excess, a solution of pure mercuric chloride 


is gradually added. The yellow precipitate is thoroughly washed 
by decantation and preserved in the moist state. 


Meta-phenylene-diamine, see Oolor Reagents, m diamido-benzol, 
page 78. 


METHYL IODIDE, C Hsl. 


Uses. Its high specific gravity, = 2.1992 at 0° C., makes it use- 
ful in a set of reagents for petrographic separation. It is also 
used for the detection of pyridine bases. A few drops of the base 
are heated in atest tube with an equal amount of methyl iodide, 
and then mixed with a little powdered potassium hydrate and a 
few drops of water. On gentle heating a peculiar penetrating 
odor indicates a pyridine base(A. W. Hofmann). C Hs3I = 141.581. 

Tests. The tests for purity need not be extended beyond identi- 
fication of boiling point and specific gravity. The commercial 
article is sufficiently pure. Methyl iodide is a colorless liquid of 
ethereal odor, spec. gr. 2.1992, at 02 C. and boils at 44°C. When 
heated with 75 parts of water it is decomposed into hydriodic acid 
and methyl alcohol. It attracts moisture from air and forms a 
crystalline hydrate. 

PREPARATION. One part of red phosphorus in small pieces and 
5 parts of concentrated wood alcohol are placed into a flask and 
gradually mixed with 10 parts of powdered iodine. The product 
of the reaction is distilled off and rectified, preserving the portion 
boiling at 44° C, 


METHYLENE IODIDE, C He Ia. 


UsxEs. On account of its specific gravity being 3.342 at 5° C. the 
liquid is used as a petrographic separator. C Hy, Ie = 267.088. 

Tests. The yellow liquid boils at 180°C., being partially de- 
composed, and congeals at 0° C., forming tabular crystals. 

PREPARATION. Fifty gr. iodoform and 200 gr. concentr. hydrio- 
dic acid are heated to 127° C.and small pieces of phosphorus 
thrown in until the liquid is no longer colored brown; then more 
iodoform and phosphorus may be alternately added, hydriodic 
acid being regenerated (Baeyer). It may be purified by freezing 
and selecting the crystals. 


O* 


136 NAPHTHALIN DERIVATIVES—NITROSO- BETA-NAPHTHOL, 


Methyl Orange, see Color Reagents, Dimethyl-amido-azo-benzol- 
sulphonic acid, page 78. 

Methyl Violet, see Color Reagents, page 85. 

Methylene aceto-chlorhydrin has been proposed by Grimauz as a 
reagent for morphine. When the reagent is added to morphine 
in powder, or dissolved in glacial acetic acid, and then sulphuric 
acid in excess, a rose-red color is produced. 

Millon’s Reagent, see Mercuric Nitrate, page 133. 

Molybdic Acid and derivatives, see page 12. 


NAPHTHALIN DERIVATIVES. 


NAPHTHOL, Ci H; O H. 


Usrs. The two varieties called Alpha and Beta-naphthol are both 
used for the detection of chloroform and chloral hydrate, which, 
with solution of naphtholin potassium hydrate, heated to about 40° 
C., give a transient blue color (Lustgarten). Both in solutionin 
cone. alcohol give various color reactions with dry powdered 
sugar and other carbohydrates (/hl). These, however, are more 
delicately shown in Molisch’s modification, by means of which very 
minute traces of sugar may be detected by alpha-naphthol (or 
naphthalin), but not by beta-naphthol. Molisch mixes a few drops 
of a 15% solution of alpha-naphtholin alcohol with the urine or 
other sugar solution, and then adds concentr. sulphuric acid, to 
form a layer beneath. At the zone of contact a violet color ap- 
pears, even if but slight traces of sugar are present. 

Tests. The commercial articles are sufficiently pure; even 
naphthalin will answer as a substitute. 

PREPARATION. A mixture of 4 parts of naphthalin and 3 parts 
conc. He S Osis kept for 12 hours at the temperature of 80° C. and 
then poured into 10 to 12 volumes of boiling water. After cooling, 
the unchanged naphthalin is filtered off and the filtrate saturated 
with lead carbonate. On evaporation the beta-salt crystallizes 
first, the alpha afterwards. The mixed salts are boiled with 12 
parts of alcohol, which dissolves the alpha, but leaves the beta- 
salt undissolved. From the separated lead salts the naphthalin- 
sulphonic acids are isolated by hydrogen sulphide. Heating with 
potassium hydrate liberates the naphthols corresponding to the 
acids. 


NITROSO-beta-NAPHTHOL, Cio He, (N O) O H, 


Uses. The solution in acetic acid serves for the separation of 
cobalt from nickel, its nickel salt being soluble, the cobalt salt in- 


or 


NICKEL AND ITS COMPOUNDS. 137 


soluble in dilute hydrochloric acid (12%); also of iron from alum- 
inium, the iron salt forming aninsoluble precipitate, which, by 
heating with oxalic acid, is converted into ferric oxide, while alum- 
inium remains in solution (llinskt and v. Knorre). Also to separ- 
ate copper from lead, cadmium, zinc, magnesium, etc (v. Knorre). 
mat: W. = 172.681. 

Tests. The compound crystallizes either in short prisms or 
thin tablets of orange-brown color; melting at 109.5° C., almost in- 
soluble in water, very soluble in ether, carbon-disulphide, glacial 
acetic acid and hot alcohol, somewhat less in cold alcohol and 
acetic acid of 50%. Its alkali salts are green; that of sodium is in- 
soluble in weak soda lye. 

PREPARATION. One part beta-naphthol and 0.75 parts of zine 
chloride are dissolved in 6 parts of hot alcohol, and, after boiling 
a short time, 0.5 parts of sodium nitrite dissolved in a little water 
is added and the boiling continued until the red-brown zinc- 
nitroso-beta-naphthol begins to separate. After 12 hours’ stand- 
ing this is filtered off and washed with a little alcohol. The zine 
salt is then diffused in 10 parts of water and gently heated with 1 
part of sodium hydrate. This dissolves the zinc, while green 
sodium-nitroso-beta-naphthol separates in crystals. After cooling, 
the sodium salt is removed by filtration, washed with dilute 
sodium hydrate solution and decomposed by cold, dilute hydro- 
chloric acid, which leaves the pure alpha-nitroso-beta-naphthol 
(llinskt and Henriques). 


NICKEL AND ITS COMPOUNDS. 
NICKEL, Ni. 


Metallic nickel is sometimes used in the form of capsules, in- 
stead of silver, for dissolving aluminium hydrate in alkaline hy- 
drates so as to separate it from ferric hydrate. Also in the form 
of wire in blowpipe work. Also for the preparation of nickel 
salts. Ni = 57.928. 


NICKELOUS CHLORIDE, Ni Cl, + 6 He O. 


Usrs. As an indicator in the volumetric determination of zine 
by sodium sulphide. Also in conjunction with potassium hydrate 
for detection of glucose, as proposed by Mazzara. 

Tests. Commercial nickel chloride is sufficiently pure for the 
above purposes. 

PREPARATION. The metal is dissolved by means of heat in hy- 
drochloriec acid and crystals obtained by evaporation. 


188 NICKELOUS SULPHATE. 


NICKELOUS HYDRATE, ozide or oxalate, are sometimes used 
in blowpipe analysis, to detect potassium in presence of sodium 
and lithium by the blue color given to the borax bead, colored 
brownish by anickel salt. The purity of the commercial article 
suffices for this purpose. The hydrate also serves for removal of 
tannin. 


NICKELOUS SULPHATE, NiS 01+ 7 He O. 


Usres. For volumetric determination of tannic acid an empyri- 
cal solution of nickelous sulphate is used with ferric chloride as 
indicator (Casali). Thé salt is also used as indicator by spotting 
in the volumetric determination of zine by sodium sulphide. At. 
W. = 279.472; anhydrous Ni S O4 = 153.752. 

Tests. Nickelous sulphate crystallizes at ordinary temperature 
in dark green, monoclinic prisms, containing 7 He O, but may be 
obtained between 380° and 40° C.in quadratic blue-green crystals 
with 6 HeQO, or at still higher temperature again in, monoclinic 
crystals with 6H, O. Hence, for quantitative work, it must be 
weighed in the anhydrous state, after drying at 270° to 300° C. Its 
solution must not become blue-black on addition of tannic acid, 
nor give a blue precipitate with potassium ferrocyanide. A borax 
bead saturated with it must not show the intense blue color of 
cobalt. 

PREPARATION. Nickel sulphate is now sold quite pure, being 
manufactured on the large scale for electro-plating. To remove 
the remaining traces of copper, iron and cobalt it may be dis- 
solved in water acidulated with a few drops of sulphuric acid, and 
digested for some time with a small bright piece of iron wire, to 
precipitate copper, if any be present. After filtering the iron is 
converted into ferric salt by heating with some nitric acid, and 
then removed by precipitating with a large excess of ammonia 
water in which nickel redissolves, leaving ferric hydrate behind. 
The filtrate is evaporated to dryness and heated to 300° C. to ex. 
pel ammonia. It is then redissolved in water acidulated with 
acetic acid and the cobalt precipitated by potassium nitrite. The 
yellow precipitate of potassio-cobaltie nitrite (Fischer’s salt) is 
allowed to subside for 24 hours and then removed by filtration. 
In the filtrate the nickel is then precipitated by sodium carbonate, 
the precipitate thoroughly washed, dissolved in sulphuric acid 
and crystallized. 

Casali’s volumetric nickel solution is made by dissolving 2.89 gr. 
of pure anhydrous nickel sulphate in boiling water acidulated 
with a few drops of sulphuric acid. After cooling, a solution of 








OXYGEN. : 139 


3) gr. of ammonium sulphate is added. The solution is divided 
into two equal parts, and to one-half ammonia water is added, 
drop by drop, until it has assumed a violet-blue color. The two 
solutions are then mixed and diluted to 1 litre. One Cc. precipi- 
tates 0.01 gr. of pure tannic acid from galls, or 0.01497 gr. of oak bark 
tannin (quercotannic acid and phlobaphen, etc.) Paper moistened 
with ferric chloride serves to indicate the complete precipitation 
of tannin. 


NITROUS ETHER or ethyl nitrite, C2 Hs .N Os, may be used, 
on account of its nitrous acid, to detect antipyrine by the green 
color of the iso-nitroso-antipyrine produced by adding to it nitrous 
ether and some free acid. Also to detect phenol and salicylic acid 
by the yellow color of the nitro-compound formed, and albumen 
by the formation of yellow xanthoprotein (Hyckmann). U.S.P. 
spir. etheris nitrosi will answer the purpose. : 


OILS are occasionally used for analytical purposes: 

Linseed oil to absorb vapors of carbon disulphide; 

Sweet almond oil as a solvent, and to differentiate in microscopi- 
cal research between coloring matters soluble in it (saffron), from 
those insoluble (safflower); 

Poppy oil to detect turpentine as an adulterant of essential oils; 

Oil of turpentine to aid in the detection of blood by guaiacum 
(Van Deen), ete. 

Osmic acid, see page 15. 


OXYGEN, O. 


Uses. Pure, dry oxygen gas is used for combustions in elemen- 
tary organic analysis. O = 15.96. 

Tests. Absolute purity from carbon dioxide and chlorine is 
requisite; hence, the gas passing through lime water and through. 
silver nitrate solution must not render them turbid. Moisture 
must be removed by passing it through dry calcium chloride, or. 
cone. sulphuric acid, or both. Nitrogen may be present from in- 
complete expulsion of air from the generating or storing appar- 
atus; its presence and quantity is ascertained by enclosing a 
measured volume of the gas in a graduated tube over mercury 
and absorbing the oxygen by potassium hydrate and pyrogallic 
acid. If no portion is absorbed by solution of potassium hydrate 
alone (C Oz), and the whole is then absorbed after introduction of 
the pyrogallic acid, the oxygen is pure; if not, the percentage of 
remuining nitrogen is noted and allowed for in calculating the re- 
sults of the combustion. 


140 PALLADIUM AND ITS COMPOUNDS, 


PREPARATION, It is best to prepare sufficient to serve for seve- 
ral occasions, so as to avoid the necessity of losing from each 
small portion the quantity necessary to expel air from the appar- 
atus. Itis made by carefully and very gradually heating an inti- 
mate mixture of 20 parts of pure potassium chlorate with one part 
of pure manganese dioxide in a copper flask with metallic delivery 
tube and ground joint connections. (See also potassium chlorate). 
A wash bottle is introduced containing a dilute solution of caustic 
soda, and the tube leading from it to the gasholder is so arranged 
that the first portion of gas generated can escape for a sufficient 
length of time to insure expulsion of air from all parts of the ap- 
paratus. The gas is then received into the holder, which is filled 
completely with water, from which dissolved gases have been ex- 
pelled by boiling. Whenthe gasis to be transferred into the com- 
bustion tube similar precautions for expulsion of air must be taken, 
as it must pass through apparatus interposed between the holder 
and the tube, which contains absorbents retaining chlorine, car- 
bon dioxide and moisture, so that only pure, dry gas may reach 
the combustion tube. Potassium chlorate yields 39.18% of its 
weight of oxygen; 100 grammes yield 27.4 litres. 

Oxygen may also be obtained from hydrogen dioxide solution 
by the addition of potassium permanganate; 100 Ce. of the usual 
3% commercial solution of H, O; furnishing one litre of oxygen 
(Goehring). 


PALLADIUM AND ITS COMPOUNDS. 
PALLADIUM, Pd. 


Uses. In gas analysis metallic palladium in the form of thin 
foil or wire, or as a finely divided metallic coating of asbestus, etc., 
serves to absorb free hydrogen from gas mixtures, and thus to 
measure its quantity by contraction of volume. This absorption 
takes place after the metal has, by heating in air, been superfi. 
cially coated with a thin film of palladious oxide. During the ab- 
sorption the metal becomes hot and cools again as soon as all the 
hydrogen has been occluded. If air be now readmitted the oc- 
cluded hydrogen unites with its oxygen, liberating heat enough to 
set the metal aglow, and, after the disappearance of the hydrogen, 
the film of oxide is restored, making the palladium ready for 
another operation. The process is conducted in a narrow glass 
tube, bent into suitable shape, interposed between the gas burette 
and pipette. Sometimes a measured volume of air is added at 
once to the mixture of gases and the’ palladium in the tube 


PALLADIOUS CHLORIDE. 141 


heated by a water bath, while the gases are slowly passed over it, 
effecting a quiet combustion of the hydrogen in contact with the 
metal (Winkler, Hempel). 

Palladium, fully charged with occluded hydrogen by connecting 

it with the positive pole of a galvanic battery and immersing it 
into dilute sulphuric acid, is used to reduce metals from their so- 
lutions, and thus to make quantitative determinations of copper 
and gold, ete. (Schwartzenbach and Kritschewsky). For these 
uses the metal furnished by the platinum affineries is sufficiently 
pure. See also palladium-asbestus, on page 46. Pd = 105.735. 
_ Tests. Pure palladium dissolves without residue in warm, fum- 
ing nitric acid. It does not yield anything soluble to cold, dilute 
sulphuric acid. In nitro-muriatic acid it dissolves without resi- 
due. 


PALLADIOUS CHLORIDE, Pd Cle. 


Usss. Palladious chloride and its double salt sodiwm-palladious 
chloride, Pd Cle. 2 NaCl, are used for detection and quantitative 
determination of iodine, which is precipitated from iodides as 
brown-black palladious iodide, Pd Js, insoluble in water, while 
bromides are not precipitated. Paper or cloth strips, immersed 
in dijute solution of palladious chloride (2 Mgr. in 1 litre of water), 
are blackened by C O, Ha S, C Hua, Ce He, H ozone and N H3(?), 
while C Oz, N, O, Cl, Ne Oz and cyanogen are without effect (Boett- 
ger, Fodor, Schneider). 

Palladious chloride and sodium-palladious chloride is also used 
for the detection, removal and quantitative determination of car- 
bon monoxide, absorbed by cuprous chloride from mixtures of 
gases. The pure solution of cuprous chloride does not affect the 
palladium solution, but as soon as it contains C O it reduces and 
precipitates metallic palladium: Pd Cle+CO-+ HzO =Pd+C 
Oo+2HCl. EKach1 gr. of Pd = 0.2641 gr. = 211 Ce. of C O. 

A mixture of the two solutions, palladious chloride and cuprous 
chloride, both saturated with sodium chloride, may be used to first 
absorb the C O and then convert it into C Oz, which may be de- 
termined by absorption in K O H in the gas pipette and thus volu- 
metrically determined (Winkler). Pd Cle = 176.477. 

Tests. Pure anhydrous palladious chloride is a brown mass, 
which attracts moisture from air; it dissolves easily in water, from 
which, on evaporation, it crystallizes in quadratic prisms, contain- 
ing Pd Cle+ 2H, O, which no longer attract water. After precipi- 
tation by an excess of pure potassium iodide from a solution acid- 
ulated with hydrochloric acid, the filtrate should not give more 


142 PALLADIOUS CHLORIDE. 


than mere traces of a precipitate with hydrogen sulphide or am- 
monium sulphide. Its solution gives a brownish precipitate with 
potassium hydrate, which redissolves on addition of an excess of 
the alkali. From this solution alcohol reduces metallic palladium. 
Ammonium chloride in concentrated solutions produces a flesh- 
colored precipitate soluble in ammonia water. 

PREPARATION. Pure palladium is dissolved in nitro-muriatic 
acid, the clear solution is evaporated to expel the excess of acid, 
then redissolved in water and crystals obtained by evaporation. 
These for use are dissolved in 10 parts of water. Sodiwm-palla- 
dious chloride is made by adding 6 parts of pure sodium chloride 
for every 5 parts of metallic palladium dissolved in the nitro-muri- 
atic acid, evaporating to dryness and dissolving in 12 parts of 
water (Fresenius). 


PALLADIUM NITRATE, Pd (N Os)2, has been proposed for the 
detection of bromides. In concentrated neutral solution it gives 
with bromides a red-brown precipitate of Pd Bre, while palladious 
chloride gives none; iodides, however, are precipitated by it, as 
well as by palladious chloride. Hence, after precipitation of the 
iodides by Pd Cle and neutralization, bromides may be detected in 
the filtrate by palladious nitrate. The method is not much in use. 
Pd (N Os)o = 229.539. 

It is made by dissolving palladium in concentrated nitric acid. 


PARAFFIN. 


Paraffin of commerce consists of a mixture of various hydro- 
carbons of the general formula Cn H en + 2, with others of the ole- 
fine series. It is sold in different states of consistence—solid, 
semi-solid and liquid (paraffin oil). The solid is sometimes used to 
prepare hydrogen sulphide by heating it together with sulphur. 
The semi-solid serves as a valuable lubricator for glass apparatus: 
ground joints, stoppers and stopcocks. Liquid paraffin is a ready 
‘ solvent of chlorine, bromine, iodine, colorless phosphorus, etc.; 
hence, it is used in the preparation of some of their compounds, 
hydriodic acid (see page 7), hydrobromic acid, phosphorus com- 
pounds and haloid ethers. With chloroform and ether it forms 
clear solutions when they are anhydrous, but turbid if they con- 
tain water; hence, it may be used to detect its presence in them 
(Leon Crismer). It absorbs gaseous hydrocarbons, and its use is, 
therefore, proposed in gas analysis (Hasenpflug). Liquid paraffin, 
as well as solid, is also used to prepare hydrogen sulphide by heat- 
ing it with sulphur (Lidof’). The liquid paraffin used for these 
purposes must be colorless, free from fluorescence, its spec. 


PARA-TOLUIDINE. 143 


grav. not less than 0.840; it must not contain volatile constituents 
boiling below 860° C. Freshly cut metallic potassium or sodium 
must not lose its lustre when immersed in it for some time. When 
kept at 100° C. in contact with cone. sulphurie acid it must not 
within 24 hours either become brown itself or communicate to the 
acid more than a light brown color. 


PARALDEHYDE, (C2 Hy O)s, has been recommended by Amthor 
for detection of caramel in wine, ete. When paraldehyde is 
added in sufficient quantity to wine colored with caramel a brown 
precipitate forms, while the liquid becomes colorless. Natural 
wines give a white precipitate. The paraldehyde of commerce is 
sufficiently pure for this reaction. 


PARA-TOLUIDINE, Ce Hs. C Hs. N Hae. 


Usss. The commercial salt, containing ortho-toluidine and ani- 
line, is used for the detection of nitric acid, even in small traces, 
as in natural waters. When a few drops of a solution of para- 
toluidine in sulphuric acid arc mixed with several Cc. of water con- 
taining anitrate, and then concentrated sulphuric acid added, so 
as to form a layer beneath, the zone of contact assumes a red 
eclor, which gradually fades into yellow. Chlorates, bromates, 
iodates, chromates and permanganates produce a blue color with 
the reagent, so intense as to hide the red of nitrates, if simultan- 
eously present. With nitrous acid the color is yellow to brown, 
according to the quantity present (Longt). The absolutely pure 
salt gives with nitric acid a blue color, which gradually passes 
into red, while the impure commercial gives the red at once. See 
also Aniline Sulphate, page 42. 


Tests. Pure para-toluidine crystallizes in colorless tables; 
melts at 45° C.; boils at 198°C. It dissolves in 285 parts of water 
at 12%. Chlorinated lime solution does not color it blue or violet, 
if aniline is absent. 


PPEPARATION. The pure salt may be made by distilling the 
commercial, preserving the fraction boiling between 195° and 205° 
C., and cooling it to 0°; this separates most of the ortho-toluidine, 
which remains liquid to —20° C. Two parts of the crystals are 
then dissolved in8 parts of boiling water; 1 part of oxalic acid is 
added and the solution cooled to 80°. Para-toluidine oxalate pre- 
cipitates, while the aniline salt remains in solution. The precipi- 
tate is filtered off, washed with ether to remove the last trace of 
ortho-toluidine, and the pure oxalate is then decomposed by dis- 
tilling with calcium hydrate. 


144 PHENOL. 


PHENOL, Ce Hs. OH. 
Carbolic Acid. 


Uses. For detecting nitric acid, by which phenol is converted 
into the intensely yellow tri-nitro-phenol, picric or carbazotic 
acid, whose color may be still more heightened by converting it 
into the ammonium salt. Drinking water or other liquids contain- 
ing traces of nitrates are evaporated to dryness and moistened 
with a drop of a mixture of 1 part phenol, 4 parts of concentrated 
sulphuric acid and 2 parts of water. In conjunction with mercur- 
ous nitrate, phenol serves to detect nitrous acid by precipitation 
of metallic mercury and a red color of the solution (Plugge). Itis 
also used for the detection of wood pulp in paper, which turns 
yellowish-green when moistened with a solution of 1 drop of liquid 
phenol in 1 Cc. of hot concentrated hydrochloric acid (Zhl). Phe- 
nol has also been proposed to detect adulterations of butter with 
other fats. Ifigr. of butter is melted with 3 gr. of deliquesced 
phenol, and then 900 Ce. of water added, and the mixture gently 
heated, the solution must remain clear and uniform, if the butter 
is pure (Crook). Conjointly with sulphuric acid, phenol serves to 
detect, by the red color produced, colocynthin (Johannson) and 
elaterin (Lindo); narceine, veratrine, codeine, etc. (Arnold); also 
sugars by a reddish-brown (Molisch). It also serves to detect gly- 
cerin in wine, ete., by heating the solution to dryness, moisten- 
ing with a drop or two of a mixture of equal parts of phenol 
and concentrated sulphuric acid and adding ammonia. A red 
color indicates glycerin (Donath and Mayrhoffer). A standardized 
solution of phenol is also used for titration of bromine, with which 
jt precipitates as tri-brom-phenol (@iacosa). 

As the violet color, which is produced when phenol is mixed with 
neutral ferric chloride, does not appear in presence of glycerin, 
this reaction may serve to detect the latter. The liquid is diluted 
with water and very little phenol is added; if, on addition of one 
drop of ferric chloride, no violet color appears, glycerin is present 
(Barbsche). 

It also, in conjunction with calcium hydrochlorite, serves to de- 
tect ammonia by a green color (Lez). 

Phenol-potassium serves for the identification of iodoform in 
urine, etc. The liquid is mixed with a little alcohol and a few 
drops of it poured upon a small quantity of phenol potassium in a 
test tube and gently heated. A red coating will cover the bottom 
of the test tube, soluble in dilute alcohol (Lustgarten). , 

Cs Hs . O H =93.804, 





PHENYL-HYDRAZINE. 145 


Tests. Pure phenol crystallizes in colorless, rhombic needles, 
melting at 40° to 41° C. Phenol hydrate, (Ce Hs .O H)z + He O, 
melts at 16°C. Presence of water or of cresol, or other homologues, 
changes the melting point. It boils at 188°. At 16° it dissolvesin 
15 parts ot water; at 87° it is miscible with it in all proportions. 
It easily dissolves in alcohol and ether. The watery solution red- 
dens litmus slightly. Traces of ammonium nitrite (often found in 
the atmosphere) color it red. With Hz S it must produce neither 
color nor precipitate. The purest white crystals of commerce, 
though not entirely free from homologues, are sufficiently pure 
for making the reactions described above. The strength of solu- 
tions is ascertained by titration with bromine. 


PREPARATION. Phenol is obtained on a large scale by fractional 
distillation of the ‘‘dead-oil” portion of coal-tar, saturating the 
product with caustic alkali to remove tarry matters, etc., decom- 
posing again by acid to separate the phenol, which is further 
purified by repeating the process and by fractional distillation. 

Phenol-potassium is made by dissolving 4 parts of potassium in 9.5 
parts of phenol, in a vessel filled with hydrogen gas to prevent 
oxidation by the atmospheric oxygen. It forms needle-shaped 
crystals, which easily deliquesce and must be carefully preserved. 


Phenol-phthalein, see Color Reagents, page 87. 
PHENYL-HYDRAZINE, Ce Hs.NH.N He. 


Usss. Phenyl-hydrazine and its hydrochlorate, CeHs. NH .N 
He . H Cl, are used for the detection of aldehydes, ketones, and es- 
pecially of sugars. The characteristic compounds formed with 
these differ in their melting points, so as to permit more special 
identification. Those with dextrose (phenyl-dextros-azon) and 
with levulose (phenyl-levulos-azon) melt at 204° C.; lactose, 200°; 
maltose, 206°; benzaldehyde (bitter almond oil) and cinnamic alde- 
hyde at 152.52; salicylicaldehyde at 142°; acetophenon at 1702, etc. (EZ. 
Fischer). For sugar in urine the reagent is especially valuable, as it 
is less liable to mislead than the various tests based upon reduction 
of metallic salts, there being no other substance in urine capable of 
producing phenyl] dextros-azon. To5 Ce. of urine a solution of 0.1 
to 0.2 gr. of phenyl-hydrazine hydrochlorate and 0.15 gr. of sodium 
acetate in 2 Ce. of water is added and heat applied for several 
minutes, when golden-yellow phenyl-dextros-azon is precipitated, 
mostly in needle-shaped crystals (Jaksch). The test has been modi- 
fied by Schwarz, who mixes 5 Ce. of urine with 5 Ce. of normal 
potassium hydrate, adds 1 or 2 drops of the free base, phenyl-hy- 
drazine, and heats to boiling. If glucose is present, the solution 


146 PHOSPHORUS. 


assumes an intense yellow or orange color. After cooling a slight 
excess of acetic acid is added, which precipitates the yellow erys- 
tals of phenyl-dextros-azon. CsH;s.N H.N He = 107.886. 

Tests. Pure phenyl-hydrazine crystallizes in tabular crystals, 
which at 23° C. melt to form a yellow, oily liquid, which only con- 
geals again at a much lower temperature. It boils at 233° 
to 234° C. In cold water it dissolves very sparingly, and is almost 
insoluble in solutions of caustic alkalies. It reduces salts of cop- 
per, silver, gold and platinum in the cold. 

Phenyl-hydrazine hydrochlorate forms small, silky tablets, easily 
soluble in hot water, sparingly in cold, almost insoluble in con- 
centr. hydrochloric acid. ~The commercial preparations are of 
sufficient purity. 

PREPARATION. Dissolve 10 gr. aniline in 200 gr. conc. hydro- 
chloric acid, cool the solution well and very gradually add a solu- 
tion of 7.5 gr. sodium nitrite in 50 Ce. water. Some sodium chlor- 
ide is precipitated, and the solution contains diazo-benzol chlor- 
ide; it is filtered and then an ice-cold Solution of 45 gr. stannous 
chloride in 45 gr. conc. hydrochloric acid is added. Phenyl-hy- 
drazine hydrochlorate is formed at once, and separates in minute 
white crystals, which are removed by filtration. From these the 
pure base may be made by dissolving in warm water, adding 
sodium hydrate sufficient to combine with the acid, removing that 
part of the oily base which separates and, finally, extracting the 
rest by shaking out with ether (V. Meyer and Lecco). 


Phloroglucin, see Color Reagents, page 87. 
PHOSPHORUS, P. 


UssEs. The ordinary colorless, transparent variety is used in 
gas analysis, in the form of thin pencils, for absorption of oxygen 
(Lindemann). Also for making various preparations of phos- 
phorus, red phosphorus, the oxides and acids, the various halogen 
compounds of phosphorus, etc.; it is also used for the preparation 


of hydriodic acid, methyl iodide, etc., for which, however, red 


phosphorus is preferable. P = 380.958. 

Tests. Pure phosphorus of the ordinary variety is of waxy con. 
sistence, transparent, colorless, or slightly yellow; it melts at 44°, 
ignites at 50°, insoluble in water, sparingly soluble in absolute al- 
cohol or ether, easily in carbon disulphide, chloroform, benzol, 
etc. The principal impurities of phosphorus are arsenic and sul- 
phur. To detect these one part of phosphorus is dissolved at 
gentle heat in 14 parts of nitric acid of 40%, spec. gr. 1.251; after 
solution the liquid is evaporated to expel nitrous fumes and sur- 


PHOSPHORUS PENTOXIDE. 147 


plus of nitric acid. The solution should now contain pure ortho- 
phosphoric acid, which may be tested as directed on page 17. No 
yellow precipitate of arsenic should be produced by protracted 
passing of H2S. Gutzett’s modification of Marsh’s test, in which 
hydrogen is produced by pure zinc and pure dilute acid in a long 
test tube, covered by a cap of filter paper moistened with a drop 
of cone. solution of silver nitrate, must, after addition of the phos- 
phoric acid solution, show no sign of arsenic during half-an-hour, 
by a yellow color of the silver spot turning to black by moisten- 
ing. In the dilute solution of phosphoric acid barium chloride 
should produce no precipitate. 

Exposure to light and air changes the external portion to an 
opaque white, while the interior turns yellow or red. 

Red phosphorus is insoluble in C 82, more stable in air, and re- 
quires 260° C. for ignition. The tests for purity applied after oxi- 
dation are the same as for the ordinary variety. 

PREPARATION. It will hardly be attempted to manufacture 
phosphorus from bone ashes on the small scale. To convert it 
into the thin pencils used in gas analysis a sufficient amount of 
phosphorus is melted under water in a capacious test tube to form 
a layer of 6Cm. indepth. Into this a narrow glass tube, slightly 
conical, is immersed with the wider end down, the top is closed 
with the finger, and tube and contents transferred to a beaker of 
cold water. The melted phosphorus shrinks in solidifying and 
drops into the beaker in the shape of a thin pencil. The product 
must be carefully preserved under water in a bottle surrounded 
by a metallic box. 

fied phosphorus is made by heating the ordinary phosphorus in a 
close tube, freed from oxygen, to 300° C. It generally contains 
some unchanged phosphorus of the ordinary variety, which may 
be dissolved out by carbon disulphide. 


PHOSPHORUS PENTOXIDE, P2 O:. 


Usrs. Phosphorus pentoxide, or anhydrous phosphoric acid, on 
account of its great affinity for water, is employed for dehydration 
of bodies containing water, or for decomposing those which con- 
tain hydrogen and oxygen. It serves to concentrate acids by with- 
drawal of water, and is, therefore, useful as an addition to sul- 
phuric acid used in Ajeldahl’s process for converting the nitrogen 
of organic bodies into ammonium salts. 

Tests. Phosphorus pentoxide forms white, amorphous flocculi, 
which, at a high temperature, sublime unchanged and without 
residue. From air it attracts moisture and liquefies. Dropped 
into water it hisses and dissolves into meta-phosphoric acid. Its 


148 ' PLATINUM. 


solution is tested for arsenic like that of phosphorus. 
PREPARATION. By burning phosphorus in a suitable apparatus 
in dry air or oxygen. 


PLATINUM AND ITS COMPOUNDS. 


PLATINUM, Pt. 


Usss. In the state of wire or foil, or wroughtinto various shaped ~ 
vessels, the metal, on account of its high fusing point (near 2,600° 
C.), serves as a support in many operations requiring high temper- 
ature, fluxions, blowpipe work, etc. Its insolubility in most acids 
renders it most valuable as material for vessels in which hydro- 
fluoric acid, concentrated sulphuric acid, ete., are distilled. Ina 
state of fine subdivision, as platinum-black or sponge or platinized 
asbestus (see page 47), it condenses up to 200 volumes of oxygen, 
and thereby serves to unite this with hydrogen or vapors contain- 
ing it. In nitro-hydrochloric acid it dissolves, and from the chlor- 
ide thus obtained other preparations are made. 

By the aid of zinc platinum foil serves to recognize antimony, 
which, when dropped upon the foil in acid solution, is reduced by 
the zinc to black metallic antimony, which closely adheres to the 
platinum foil. Pt = 194.415. . 

Cautions in using platinum vessels. Many substances, when 
brought in contact with metallic platinum, are capable of injuring 
it, either by alloying with it at high temperature or by corroding 
or dissolving it. Hence, neither chlorine nor compounds capable 
of evolving it must be treated in platinum vessels. Caustic alka- ~ 
lies, especially lithium and mixtures from which they may result, 
are liable to corrode platinum vessels in which they are fused, un- 
less air can be absolutely excluded from them (it is supposed that 
a peroxide forms, to which the corrosion is due). Alkaline nitrates, 
sulphides, phosphides, cyaniaes, metals or metallic sulphides, 
oxides or organic salts, from which metals may be easily reduced, 
are likewise injurious. When it is necessary to heat a platinum 
crucible in a charcoal or coke furnace, it must be encased in cal- 
cined magnesia, contained in a Hessian crucible, to avoid direct 
contact with the fuel. Over a gas or alcohol lamp it may be heated 
in direct contact with the flame, provided it be supported on a 
triangle of platinum wire, so as to avoid contact with other 
metallic support at high heat. To clean platinum crucibles 
or capsules from material closely adhering after fluxions, etc., 
scouring with round sea sand, or fusing in them borax or acid po- 
tassium sulphate, may become necessary. They should be occa- 





PLATINIC CHLORIDE—CHLORO-PLATINIC ACID. 149 


sionally burnished to prevent scaling and formation of fissures; 
for this purpose a wooden block, fitting accurately into the vessel, 
is very useful, as it gives a firm support and enables the restora- 
tion of indented parts into perfect shape. 


PREPARATION of platinum ina fine state of subdivision. That 
of platinum asbestus, by means of reduction of platinic chloride 
by a salt of formic acid, is already described on pages 46 and 47. 

Platinum black ismade by reducing platinum chloride, either by 
metallic zinc, etc., or better, by reducing platinum chloride, dis- 
solved in glycerin by boiling with sodium hydrate, washing thor- 
oughly and drying. 

Platinum sponge is made by precipitating platinic chloride by 
ammonium chloride, forming the yellow double salt, Pt Cla. 2. N Hg 
Cl, which is washed and ignited, and thus leaves the metal asa 
gray, coherent mass of somewhat less fineness of subdivision than 
platinum black. 


PLATINIC CHLORIDE, Pt Cli, and CHLORO-PLATINIO ACID, 
He Pt Cle + 6 Hz O. 


UsEs. Under the name of platinum chloride both of the above 
preparations are used indiscriminately. The commercial article, 
dry or in solution, generally contains chloro-platinic (or platino- 
hydrochloric) acid, which differs from the neutral Pt Cl4 by an ad- 
ditional 2 H Cl+6H:20O. They serve for the detection and quan- 
titative determination of potassium, rubidium, cesium, ammon- 
ium and thallium, which areprecipitated as chloro-platinates (usu- 
ally called double salts), insoluble in alcohol, while the sodium 
salt is very soluble, but may be recognized by its crystals under 
the microscope. They are also used for the detection and quanti- 
tative determination of many alkaloids, which are precipitated as 
insoluble chloro-platinates, while others (atropine, aconitine, vera- 
trine) are soluble. A few drops of the solution added to pure zinc, 
cadmium, etc., render them more soluble in acids by the establish- 
ment of galvanic action. An empirical volumetric solution of 
sodium chloro-platinate in dilute alcohol is used for titration of 
potassium salts; 12 to 15 gr. of the sodium salt are dissolved in 100 
Cc. of 50% alcohol, and its effective titre ascertained by pure potas- 
sium nitrate. It is then used for addition to specimens to be 
tested, the potassium chloro-platinate separated, and in the filtrate 
the platinum is first precipitated by zine and then the residue of 
chlorine determined by silver nitrate. The difference in the chlor-: 
ine of the chloro-platinate added and that of the residue left after 
precipitating the potassium aa realy admits of the calculation 


150 POTASSIUM AND ITS COMPOUNDS. 


of potassiumopresent (Dubernard). Pt Cl4= 335.895; He Pt Cle = 
408.635; He Pt Cle + 6 He O = 516.395. 

Tests. Pt Cl4 forms brown deliquescent masses, solublein 8 parts 
of absolute alcohol. It is capable of crystallizing with 5 He O in 
red crystals; at 100° C. these lose 1 mol. water and turn byown. 
From its solution in hydrochloric acid red needles of chloro-pla- 
tinic acid crystallize with 6 mol. water. These, by heating, lose, 
first, water and hydrochloric acid, then chlorine, forming at 225° 
dark-brown platinous chloride.. Protracted ignition dissipates all 
chlorine and leaves metallic platinum, which, if the salt was pure, 
should yield nothing soluble to nitric acid. Salt, containing pla- 
tinous chloride, Pt Cle (by over-heating in drying), leaves a green- 
ish-brown residue when dissolved in alcohol. 


PREPARATION. Metallic platinum, cut into small chips, is first 
boiled in nitric acid to remove any substance soluble in it; it is 
then washed, dried and boiled in hydrochloric acid. After again 
washing and drying, 1 part is placed into a flask with 7 parts of 
hydrochloric acid of spec. gr. 1.16, and heated to 80° C.; 14 parts of 
nitric acid are then added insmall portions, 10 or 12 drops at atime, 
and time given for the reaction to be completed, until all but a 
very small residue is dissolved. Thesolution is filtered into a por- 
celain dish and evaporated at 100° C. until the residue solidifies on 
cooling. To decompose a small rest of nitric acid yet present, a 
small amount of hydrochloric acid is added and the solution again 
evaporated; it is then redissolved in some water and again evapo- 
rated, as long as acid vapors escape. The residue is then dissolved 
in enough water to make the solution contain 5% of metallic pla- 
tinum (Post). 


POTASSIUM AND ITS COMPOUNDS. 


NOTE. In a great many analytical operations it is immaterial whether 
the salts of potassium or those of sodium with the same acid are employed, 
making in quantity due allowance for the difference in atomic weights, 
Hence, the description of uses, tests and preparation of potassium com- 
pounds, to a great extent, apply to those of sodium as well, and need not 
there be fully repeated. It is only when metallic bases are to be removed 
or detected without introducing sodium, or when acids are to be detected 
which, as tartaric acid, form difficultly soluble salts with potassium, but 
not with sodium, that sodium compounds can not be substituted for those 
of potassium. 


POTASSIUM, K. 


Usrs. Metallic potassium serves to detect nitrogen in organic 
substances by uniting, at high temperature, with it and carbon to 
form potassium cyanide (Lassaigne). This method does not apply 


° 





\ POTASSIUM ACETATE. 151 
> go & 

to Aiazorcompcads, whose nitrogen volatilizes before the metal 
can act (Graebe). Potassium may also be employed, either alone 
or as amalgam, for the reduction of many compounds, but for this 
the cheaper sodium is generally preferred. In absolute alcohol it 
dissolves, while hydrogen escapes, forming: potassiwm ethylate, K . 
C2 Hs O, which is sometimes used for the reduction of nitro-com- 
pounds (Maumene). K = 39.019. 


Tests. Metallic potassium is of silver-white lustre, of spec. gr. 
0.86; it melts at 62.5° C., and between 719° to 731° is converted into 
green vapor. It rapidly attracts oxygen from air, water, ice, etc., 
and must, therefore, be preserved under petroleum naphtha. 
Thrown on water it ignites and forms hydrate, which dissolves. 
In air it burns with violet flame, visible through blue glass or in- 
digo solution. This flame, observed with the spectroscope, should 
show the pure spectrum, free from sodium and other lines. For 
analytical purposes the metal of commerce is sufficiently pure. 

PREPARATION. On the large scale, by heating to bright redness, 
in a suitable iron distilling apparatus, a mixture of potassium car- 
bonate and charcoal, such as is obtained by charring cream of tar- 
tar. Great caution is necessary to guard against explosions. The 
metal may be redistilled in a current of dry hydrogen. 


POTASSIUM ACETATE, K . Cz Hs Ox. 


Usrs. For the detection and separation of tartaric acid in wine, 
etc. Also, instead of sodium acetate in the Kakodyl test for ar- 
senic (Cadet). In this, by infusing arsenic trioxide with an acetate 
the malodorous diméthyl arsine is formed. Also for the various 
other reactions instead of sodium acetate, when the introduction 
of sodium is to be avoifled. Mol. W. = 97.887. 


Trsts. Potassium acetate isa very deliquescent, colorless salt, 
soluble at 15° C. in 0.4 parts of water and in 4 parts of alcohol. 
When brought in contact with concentrated sulphuric acid it does 
not color it brown, unless it contains organic impurities derived 
from tarry matters of pyroligneous acetic acid. Neither hydrogen 
sulphide, ammonium sulphide, sodium carbonate, potassium ferro- 
cyanide, silver nitrate nor barium chloride should render the solu- 
tion turbid or produce in itany color. No effervescence should occur 
with aceticacid. After addition of an excess of hydrochloric acid 
and evaporation to dryness, it must redissolve in water without 

- residue. The flame colored by it should show no sodium line in 
_ the spectroscope. 
' PREPARATION. Neutralize pure potassium di-carbonate (or car- 
_ bonate with pure acetic acid), evaporate and crystallize, 
1% 


152 POTASSIUM BROMATE,. 


POTASSIUM BROMATE, K Br Os. 


Uses. To make solution of bromine for the volumetric deter- 
mination of phenol according to Koppeschaar’s method. As bro- 
mine is too volatile to keep titre for any length of time, the solu- 
tion is prepared only as needed by mixing equal volumesof a 
solution containing 0.01 of the molecular weight of K Br Os, ex- 
pressed in grammes, = 1.668 gr. in 500 Ce. of water, and of a solution 
containing 0.05 Mol. W. of K Br = 5.939 gr. in500 Cc. The litre of 
liquid thus mixed contains 4.786 gr. of bromine, which is liberated 
by a sufficient amount of hydrochloric or caiphiuris acid, and is 
capable of converting 0.01 Mol. W. = 0.988 gr. of phenol into tri- 
brom-phenol. When 50 Ce. of each solution are mixed and added 
to 0.988 gr. of pure phenol and 5 Ce. of acid, the whole amount is 
converted and no residue of bromine left, but if the phenol con- 
tained impurities then only part of the 100 Ce. of solution expends 
its bromine, and the residue is measured by adding K I and starch, 
and determining the liberated iodine by deci-normal sodium hypo- 
sulphite. The process may be so modified, that the bromine solu- 
tion is added to the phenol and acid from a burette until all phenol 
is precipitated and the percentage read off directly, paper moist- 
ened with starch and zinc iodide being used as indicator. Other 
modifications are used. Thus, Allen makes the mixture of the salts 
by saturating a hot solution of alkaline hydrate (potassium or so- 
dium) with bromine, evaporating to dryness and adjusting the titre 
of the solution by pure phenol. Sodium salts,in proper propor- 
tion, are frequently used in the place of those of potassium. K Br 
Os = 166.667 (K. Br = 118.787; Na Br Oz =150.646; Na Br = 102.766). 


Tests. Potassium bromate crystallizes in the hexagonal system, 
forming rhombohedra closely resembling regular cubes. At 15° it 
requires ahout 18 parts of water for solution; at 100°C. only 2.1 
parts. At 850° C.it melts, and a higher heat gives off all its oxy- 
gen and becomes K Br. It is best tested for purity by titration 
with silver nitrate. When 1.66667 gr. are dissolved in water it 
requires 100 Cc. of deci-normal silver nitrate to precipitate them 
as Silver bromate. Or if the same quantity of salt be first deprived 
of oxygen, by heating in a platinum crucible, the solution requires 
100 Ce. of deci-normal silver nitrate to form silver bromide, if the 
salt was pure. 


Or else 1.66667 gr. are dissolved in water, 2 gr KI, starch and a 
slight excess of hydrochloric acid are added and then titrated with 
deci-normal sodium hyposulphite (ioe Pure salt requires 
exactly 100 Ce, 





PoTASSIUM BROMIDE—CARBONATE, 153 


PREPARATION. Four parts of potassium carbonate are dissolved 
in 8 parts of water and 1 part of bromine added; chlorine gas is 
then passed through the mixture. Crystals of potassium bromate 
separate and are recrystallized from boiling water. 


POTASSIUM BROMIDE, K Br. 


Usrs. For the preparation of bromine solution (see bromate); 
also of hydrobromic acid; also for the detection of small quantities 
of copper (Hndemann and Prochazka); a crystal of potassium bro- 
mide is thrown into the solution and then cone. sulphuric acid 
added, if copper be present, the crystal surreunds itself by deep- 
red cupric bromide. K Br = 118.787. 


Tests. Pure potassium bromide crystallizes in colorless or 
white cubes. At 20° C. it dissolves in 1.55 parts of water, at 100° in 
0.98. Moist red litmus paper must not be turned blue by it. Ad- 
dition of dilute HzS O4must produce neither effervescence nor 
yellow color. When ferric chloride or chlorine water are added 
to its solution, starch added to it must not be colored blue, nor 
chloroform shaken with it assume a violet color. When distilled with 
potassium dichromate and sulphuric acid, no chlorochromic acid 
must pass into the distillate, as shown by its remaining colorless 
when saturated by ammonia. To the flame it must not communi- 
cate the yellow color of sodium. The absence of other metals is 
shown as in potassium acetate. 1.1879 gr. must require exactly 100 
Ce. of deci-normal silver nitrate for precipitation. 


PREPARATION. On the large scale, either by double decomposi- 
tion of ferrous bromide and potassium carbonate, or by adding 
bromine to potassium hydrate, decomposing by charcoal and heat 
the bromate formed and crystallizing. Either process may be used 
on the small scale, or pure hydrobromic acid may be neutralized 
by pure potassium carbonate and crystallized. 


POTASSIUM CARBONATE. 
a. NEUTRAL POTASSIUM CARBONATE, Ke C Os. 


Usss. For the precipitation of many metallic bases, some of 
which may be recognized by characteristic colors. For neutraliz- 
ation of acids. Mixed with sodium carbonate it serves as a flux 
for the decomposition of insoluble silicates, titanates, barium salts, 
etc., the mixture fusing at a lower temperature than either of the 
constituents unmixed. Also in blowpipe operations, instead 
of sodium carbonate, to detect sulphates by the hepar test, to re- 
duce metals, etc. Also in various tests for glucose (Boettger’s, 


154 POTASSIUM CARBONATE. 


Mulder’s etc.) to render liquid alkaline. Also for the preparation 
of various compounds of potassium and as volumetric solution in 
acidimetry. K,C Os = 187.892. 


Tests. Potassium carbonate is rarely sold in crystals, (K, C 
Os)2 + 8 He O; generally as a coarse, white powder, very deliques- 
cent, soluble in 1 part of cold and # parts of hot water. Its solution 
must not yield a precipitate with ammonium carbonate or sulphide. 
After slightly supersaturating with acetic acid it must give no pre- 
cipitate with H, 8, Ba Cl, or Ag N Os. The absence of arsenic 
must be proven by Flewtmann’s test (page 14) or Guwtzeit’s (see 
H Cl, page 8; Fe S, page 117; Mg, page 124; Ag N Os; Zn). With 
silver nitrate the solution must give a pure white precipitate, 
which neitherdarkens by gentle heating nor leaves any residue 
on addition of an excess of nitric acid. With di-phenyl-amine or 
pyrogallol and sulphuric acid it must not show the color of 
nitric acid. After acidulating with H Cland evaporating to dry- 
ness the residue must completely redissolvein water (abs. of silica)- 
Ammonium molybdate must not give a precipitate in the solution 
acidulated by nitric acid. When the solution is gently heated with 
a few drops of ferric chloride and ferrous sulphate solution it must 
not yield a blue color on acidulation with hydrochloric acid. The 
flame color must be violet, showing absence of sodium. 


PREPARATION. The purest salt is prepared from cream of tartar, 
purified first by repeated recrystallization, and then by digesting 
for some hours on a water bath with anequal weight of water con- 
taining 3% of H Cl. The mass is then placed upon a funnel, closed 
with alight prop of asbestus, filter paper or cotton, and washed 
by covering it with a disk of filter paper, upon which cold water is 
poured repeatedly, in small portions, until silver nitrate fails to 
show H Clin the wash water. The purified cream of tartar is then 
dried and incinerated in a clean, iron dish, either alone or after 
mixing with half its weight of pure potassium nitrate. The charred 
mass is leached out with water, filtered and evaporated until it be- 
gins to show a solid crust. It is then cooled and the crystals of 
potassium carbonate are drained on a funnel, rinsed with a little 
water and then dried. An article pure enough for most purposes 
is obtained by recrystallizing commercial potassium di-carbonate 
(bi-carbonate), washing the crystals upon a funnel until after acid- 
ulation with nitric acid the wash water is no longer rendered turbid 
by barium or silver nitrate, and then heating them above 106° C. 
up to 190° in asilver or platinum dish, until half of the carbonic acid 
is expelled and pure neutral carbonate left. The solution is gene- 
rally made to contain 10 %. For fluxing, 5.3 parts of anhydrous 





POTASSIUM CHLORATE. 155 


Sodium carbonate are thoroughly mixed with 6.9 parts dry potas- 
sium carbonate. 

Normal solution contains 68.946 gr. in 1 litre, but can not be 
made by direct weighing, unless the salt is ignited just before 
weighing and not permitted to attract moisture. It is made by 
adjusting by dilution the titre of a stronger solution, so as to cor- 
respond with normal acid solution, methyl orange being used as 
indicator. 


b. ACID POTASSIUM CARBONATE, K H C Os. 
(Di or Bicarbonate.) 


Usrs. For the preparation of Soldaini’s reagent for glucose (see 
page 93); for introduction of carbonic acid into combustion tubes, 
in Dumas’ method for determining nitrogen in organic compounds, 
by heating the salt to a temperature between 1068 to 190° C., when 
it parts with C O2 and He O, while Ke C Osis left behind (2K H C'Os 
= KeC Os: + C O2-+ Hy, O). Also for separation of the quinine 
group of alkaloids, which from acid solutions are precipitated by 
potassium acid carbonate, from the strychnine group, which are 
not thus precipitated. Also for the preparation of pure potassium 
carbonate and other salts. K H CO3 = 99.873. 

Tests. Potassium dicarbonate crystallizes in colorless mono. 
clinic prisms, soluble at 15° in 4 parts of water. When entirely free 
from neutral carbonate it does not attract moisture from the air, 
nor does its solution in 20 parts of cold water precipitate magne- 
sium sulphate. For the preparation of pure potassium compounds 
it must stand the tests as described for potassium carbonate; for 
most puposes the commercial salt is sufficientky pure. 

PREPARATION. Potassium carbonate is dissolved in about 3 
parts of water, and a slow current of earbonic acid gas is passed 
through it for several days. Large crystals of dicarbonate form, 
and are drained and purified as directed for the preparation of po- 
tassium carbonate, page 154. Or pure, dry potassium carbonate, 
made from cream of tartar, is exposed for some time to an atmos- 
phere of carbon dioxide. It is then dissolved and erystallized, if 
necessary, taking, however, great care to use no heat, asin so- 
lution the dicarbonate loses C Oz, and is converted into the neutral 
salt much below the boiling point. 


POTASSIUM CHLORATE, K CI 0s. 


Usrs. For preparing oxygen gas (page 139). Potassium chlorate 
melts at 359° C., and at a somewhat higher temperature is decom- 
posed into oxygen, potassium chloride and perchlorate, which, at a 


156 POTASSIUM CHROMATE. 


still higher heat, also loses its oxygen and is converted into chlor- 
ide. When about 5% of Mn Os, Pb O2 or Cu O are mixed with the 
chlorate it yields its oxygen at from 260° to 270° C. It is also used 
in forensic analysis together with hydrochloric acid to destroy or- 
ganic matters, so as to prepare the way for examination for metal- 
lic poisons (Fresenius and Babo). K Cl Os = 122.269. 

Trsts. Potassium chlorate crystallizes in the monoclinic (mono- 
symmetric) system, mostly in colorless, transparent tables. It is 
soluble in 16.7 parts of water at 15°C. and in1.75 parts at 100°. Its 
dilute solution is neutral to test papers, and must not give pre- 
cipitates with hydrogen sulphide, barium chloride, silver nitrate, 
ammonium oxalate or potassium ferroeyanide. After ignition on 
platinum foil the residue must be completely soluble in water, of 
neutral reaction and give no precipitate with mercuric chloride. 
It must show no trace of arsenic by the most sensitive tests. 

PREPARATION. On the large scale, by Graham’s process of satu- 
rating with chlorine gas a moist mixture of 1 molec. potassium 
carbonate with 8 mol. of calcium hydrate, leaching out with water, 
filtering and crystallizing. Or from 1 mol. potassium chloride and 
3 mol. calcium hydrate and chlorine. On a small scale it may be 
made by passing pure ehlorine through a hot concentrated solu- 
tion of pure potassium hydrate or carbonate. The crystals sepa- 
rate and are purified by recrystallization. 


POTASSIUM CHROMATE, K, Cr Ou. 


Uses. For the precipitation of barium and strontium and their 
separation, as strontium chromate is soluble, barium insoluble in 
acetic acid (J. Lawrence Smith). For detection of silver, lead and 
mercurous salts, which give precipitates of characteristic color. 
As a test for barium dioxide, etc., by production of blue color. As 
indicator in the titration of chlorides, etc., by silver nitrate (Mohr). 
In deci and centi-normal solution, containing 9.6948 gr. and 0.969 
gr. Ke Cr Og in the litre, for adjusting the titre of volumetric solu- 
tion of iodine (ZL. Crismer), and of sodium hyposulphite (Zulkow- 
sky). Ke Cr O4 = 193.887. 

Tests. Potassium chromate crystallizes in yellow, rhombic 
pyramids, isomorphous with K, S Ou, soluble at 15° in 1.65 parts of 
water. At high heat it melts without decomposition. Metallic im- 
purities are detected in similar manner as in other potassium salts. 
Of other acids it is most likely to contain sulphuric and hydro- 
chloric. Its solution in dilute hydrochloric acid must give no pre- 
cipitate with barium chloride. The precipitate produced by silver 


nitrate in its aqueous solution must completely redissolve in nitric 
acid. 





POTASSIUM DICHROMATE. by 


PREPARATION. Fifteen parts of potassium dichromate are dis- 
solved in water and 7 parts of dry potassium carbonate added. 
The solution is concentrated by evaporation and set aside to erys- 
tallize. Any dichromate remaining undecomposed is deposited 
first; as soon as only yellow crystals begin to form the motherlye 
is poured off, and from it the neutral chromate is obtained and 
purified by recrystallization. 


POTASSIUM DICHROMATE, Ke Cre O7. 


Users. Potassium dichromate (bichromate or acid chromate) is 
used for separation of barium from strontium, asin aqueous or 
acetic acid solution it forms a precipitate with barium, but not with 
strontium (J. Lawrence Smith). Also for detecting lead, silver and 
mercurous salts; also hydrogen dioxide and dioxides producing it 
by the blue color of perchromic acid, soluble in ether. Also as a 
test for alkaloids, either as Lwchini’s reagent, a saturated solution 
in hot concentrated sulphuric acid, which produces characteristic 
appearances with several alkaloids and glucosides, or in saturated 
aqueous solution, or in the dry state with concentrated sulphuric 
acid. By the latter method strychnine gives the characteristic 
series of color changes from deep blue through shades of violet 
and purple to a final yellowish-red. Aniline with similar treat- 
ment produces a blue color, which soon disappears. Atropine, 
heated with dichromate and sulphuric acid, emits the odor of bit- 
ter almonds; amyl alcohol is converted into valerianic acid; 
malates give the odor of fresh apples (Papasogli and Poli). In aque- 
ous solution it produces with benzidine a deep blue precipitate, in- 
soluble in most solvents (Juliws). Itis also used for the oxidation 
of carbon and its determination as C Og in the McCreath-Uligren 
method of iron analysis (see cupri-tetrammonium chloride, page 
100), and for estimation of cellulose (Cross and Bevan); great care 
must be taken to avoid the inaccuracies arising from imperfect 
oxidation to C Oinstead of C Oz. In microscopical examinations 
it serves not only for hardening tissues, but also as a reagent for 
differentiating various tannic acids, etc. (Sanic, Nickel). In or- 
ganic analysis it also serves to oxidize sulphur. In volumetric 
analysis a deci-normal solution containing 14.6888 gr. Ke Cre O7 in 1 
litre is used to convert 16.7734 gr. of iron from ferrous into ferric 
salt, potassium ferricyanide serving as indicator by spotting 
(Penny, Schabus). Sometimes the solution is made with 4.896 gr. 
in 1 litre, being 4 of the deci-normal strength, so that if 5.591 gr. of 
iron be weighed as a specimen each Cc. corresponds to 1 % of Fe. 
Centi-Normal solution is also used. Normal solution, containing 


158 POTASSIUM CYANIDE. 


146.888 gr. in 1 litre, is used in alkalimetry with phenol-phthalein as 
indicator (Richter), having the same value as equal volumes of nor- 
mal sulphuric, oxalic and other acids. Ke Cre O7 = 293.776. 

Tests. Pure potassium dichromate forms large, red triclinic 
(asymmetric) prisms or tables, soluble in 10 parts of water at 15°, 
in 1.1 parts at 100° C. Ata low red heat it fuses; at white heat it is 
decomposed into oxygen, chromic oxide and yellow neutral chro- 
mate. It should conform to the same tests for purity as the neu- 
tral chromate, and 14.689 gr. should require exactly 100 Cc. of nor- 
mal potassium hydrate for neutralization. 


PREPARATION. Commercial salt is dissolved in 10 parts of hot 
water, and if sulphates are found present they are removed by add- 
ing a little baryta water, mixing thoroughly and setting aside for 
some hours before filtering. For the removal of chlorides, freshly 
precipitated oxide of silver is used in similar manner. The fil- 
tered solution is then concentrated and very small crystals obtained, 
these are drained, washed and recrystallized. Before weighing 
out for making volumetric solutions the salt is fused to remove 
moisture accidentally enclosed. For ordinary qualitative work a 
10% (saturated) solution is used. A special solution for detection 
of strychnine is made by dissolving 0.01 gr. potassium dichromate 
in 5Cce. water, and adding 15 gr. (8.15 Ce.) sulphuric acid of spec. 
gr. 1.84. After cooling, the solution of these proportions gives 
better results than others by the greater permanence of the blue 
color (Flueckiger). 


POTASSIUM CYANIDE, KC N. 


Usss. Dry potassium cyanide is used at high temperature as an 
active reducent of metals not so easily reduced by other means, 
especially of tin, antimony, arsenic, etc., from their oxides and 
sulphides. In blow pipe analysis it serves, mixed with sodium car- 
bonate, for many reductions on charcoal. Also, to detect sulphur, 
sulphides and sulphates by the production of rhodanate (sulpho- 
cyanate). In solution it serves for the precipitation of metals, 
some of which redissolve, forming double cyanides, while others 
do not. Of the soluble ones, some are again precipitated by acids 
(Ni, Zn, Mn, Cd, Cu, etc.) as cyanides, or as hydrates by addition 
of bromine or chlorine (nickel), while iron and cobalt are, by boil- 
ing with asurplus of potassium cyanide (in presence of some free 
hydrocyanic acid), converted into compound cyanides, which 
are not precipitated either by acids, bromine or chlorine. Upon 
this behavior depends the application of K C N for the separation 
of cobalt from nickel. Potassium cyanide dissolves cupric sul- 


POTASSIUM CYANIDE. 159 


phide, but leaves cadmium sulphide undissolved, thus permitting 
the separation of these metals. From a solution of their double 
cyanides, ammonium sulphide precipitates zinc, but not nickel, 
and is therefore used in Wvehler’s method for their separation. In 
electrolytic analysis potassium cyanide serves to prepare solution 
of gold, ete. It is also used for the titration of copper ores by 
Parkes’ method, the copper being dissolved in ammonia and am- 
monium carbonate (Fleck, Jeller). It also serves to detect picric 
acid by the red color of the isopurpuric acid formed. Also to dis- 
tinguish gallic acid, which it colors red, from tannic acid, which is 
not colored (Young). KCN = 65.014. 


Tests. When crystallized by fusion and slow cooling or from 
alcoholic solution, potassium forms regular octohedra or cubes. It 
is generally sold in fused masses or granules, easily soluble in 
water, slightly in absolute alcohol. The aqueous solution rapidly 
decomposes, forming ammonia and potassium formate. If fused 
with access of air it always contains cyanate, and the commercial 
article is seldom free from this and carbonate. It may, however, 
be used for many purposes, if free from sulphur and silicic acid. 
It must yield with lead acetate a pure white precipitate, and with 
ferric chloride must not give a red solution. After acidulation 
with hydrochloric acid and evaporation to dryness, the residue 
must completely dissolve in water. For separation of metals a 
pure salt must be employed, which, in addition to above tests, and 
those directed to show absence of metallic impurities in all potas- 
sium salts, must show especially absence of chloride, cyanate and 
carbonate. Hence, the precipitate occasioned in its solution by sil- 
ver nitrate must be completely dissolved in nitric acid. Cyanate 
is discovered by heating the aqueous solution and then adding po- 
tassium hydrate, when ammonia will be evolved, derived from de- 
composition of the cyanate. Carbonate is shown by the gas liber- 
ated by dilute hydrochloric acid, rendering limewater turbid. 


PREPARATION. On the larger scale potassium cyanide is made, 
according to Liebig’s method, by drying yellow potassium ferro- 
cyanide, free from sulphate, by gentle heat, so as to render it an- 
hydrous, mixing 8 parts with 3 parts of dry potassium carbonate, 
and fusing the mixture at a low red heat in an iron vessel, well 
covered to prevent access of air, until the yellow color has entirely 
disappeared, and pouring the fused mass, after subsidence of the 
finely divided iron, into suitable vessels. To purify this, the ordin- 
ary commercial salt, it is dissolved in 50% alcohol, filtered and ob- 
tained dry by evaporation. An absolutely pure product for sepa- 
ration of metals is obtained by passing the vapors of hydrocyanic 


160 POTASSIUM FERROCYANIDE, 


acid, as they come from the retort into an alcoholic solution of 
pure potassium hydrate. This is evaporated and kept in the dry 
state, as the solution rapidly decomposes, even at ordinary temper- 
atures. 


POTASSIUM SILVER CYANIDE, Ag CN .KCVN, is occasion- 
ally used to precipitate quinine, quinidine, cinchonine, cinchoni- 
dine and other alkaloids. As it very rapidly spoils, the solution is 
made when needed by adding to a concentrated solution of silver 
nitrate one of potassium cyanide until the silver cyanide at first 
precipitated is completely redissolved. 


POTASSIUM CUPRIC CYANIDE, Cu (CN)z. 2K CN, has been 
used for a similar purpose as the silver salt, but is less stisfactory; 
it is made, like the preceding, only when needed from cupric sul- 
phate and potassium cyanide. 


POTASSIUM PLATINUM CYANIDE, Pt(C N), +2KCN+3 
H2 O, is sometimes used for the precipitation of the salts of alka- 
loids as platino-cyanides; free alkaloids are not precipitated 
(Schwarzenbach, Delffs). It is made by heating equal parts of 
spongy platinum and potassium ferro-cyanide to a low red heat, 
extracting the fused mass with water and crystallizing. It forms 
long prisms, blue in reflected, yellow in transmitted light. 


POTASSIUM FERROCYANIDE, Ks Fee” (C N)i2 + 6 He O. 


Uses. Potassium ferrocyanide, or yellow prussiate, forms pre- 
cipitates with many metals, some easily identified by characteristic 
colors: white, Ag, Al, Bi, Ca, Cd, Hg, Mn, Pb, Sb, Sn; yellowish- 
white, Mg; greenish-white, Ni; green, changing to gray, Co; white, 
changing to blue ferrous; dark blue ferric; red-brown Cu, uranic; 
brown uranous, Mo. Some of these are decomposed by alkalies, 
others are not. Hence, a method of separating iron from mangan- 
ese by adding citric acid and ammonia to their mixed ferrocyan- 
ides; ferric salt is decomposed by the ammonia and dissolves in the 
citrate; manganese remains unaffected (Blum). In gallium salts the 
precipitate only falls in presence of excess of H Cl (Lecocg de Bois- 
baudran). Sometimes a volumetric solution is used for titration 
of zine (Galetti). Kg Feo’ (C N)w + 6 He O = 848.678. 

Tests. Potassium ferrocyanide crystallizes in transparent yel- 
low monoclinic tables, whose angles so nearly approach the square 
(89° 27’) that, until recently, they were assigned to the quadratic 
system (Wyrouboff, Groth). At 15° it dissolves in 4 parts, at 100° in 
2 parts of water; insoluble in alcohol. Sunlight gradually decomposes 
the solution, depositing prussian blue. The water of crystallization 


bay 


POTASSIUM FERRICYANIDE. 161 


is lost below 100°; fusion converts it into potassium cyanide, iron 
carbide and nitrogen: Ks Fee” (C N)iz = 8 K CN + 2 Fe Co+ 2 No. 
For most purposes of analysis the recrystallized commercial salt is 
sufficiently pure; absence of sulphates is proven by barium chlor- 
ide, whose precipitate must redissolve in hydrochloric acid or in 
much boiling water. 

PREPARATION. The commercial salt is purified by adding to the 
solution sufficient baryta water to precipitate sulphates, filtering 
and repeatedly crystallizing. One part is dissolved in 12 parts of 
water, and the solution, as well as the dry salt, preserved in dark 
bottles. 


POTASSIUM FERRICYANIDE, Ke Fe’: (C N)iz. 


Uses. Potassium ferricyanide, or red prussiate, is by light and 
other reducents easily converted into the yellow salt; hence, it 
serves, especially in alkaline solution, to oxidize alcohol, oxalic 
acid, carbohydrates, indigo and other organic substances; also 
phosphorus to phosphoric, sulphur to sulphuric acid. With nitro- 
gen dioxide it forms nitric acid, being at the same time converted 
into nitro prusside. It is mostly used to detect ferrous salts by 
precipitation of Turnbull’s blue, manganese by a brown, nickel by 
a brownish-yellow, cobalt by a red-brown precipitate. If to the 
cobalt solution ammonium tartrate or chloride and then free am- 
monia is added and then ferricyanide a deep-red solution results, 
capable of detecting traces of cobalt in presence of nickel (Skey, 
Gentl). Inconjunction with sulphuric acid ferricyanide serves to 
detect aniline by a blue to purple color (Letheby). Its solution 
mixed with ferric chloride forms a brown solution of ferric ferri- 
cyanide, which, by reduction to prussian blue, serves to detect 
morphine and other alkaloids and reducing ptomaines. Kg F’” 
(C N)is = 657.880. 

Tests. Potassium ferricyanide forms deep-red, rhombic crys- 
tals of long, tapering columns, with almost a square base. Itis 
soluble in 2.6 parts of water at 15° C.; in 1.3 at 100°. Its solution 
is rapidly decomposed by light, while fresh it must give a clear 
brown solution with ferric chloride. 

PREPARATION. Five parts of the yellow ferro-cyanide are dis- 
solved in 50 parts of water, thoroughly mixed with 1 part of bro- 
mine and set aside ina dark place (or the solution is fully satu- 
rated with chlorine gas) until a drop of the solution no longer pro- 
duces a blue color with ferric chloride. The solution is then evapo- 
rated to about one-fifth of its volume and set aside to crystallize. 
The crystals are drained and purified by recrystallization, All 


162 POTASSIUM HYDRATE, 


operations and the preservation must strictly exclude light. Solu- 
tion is made only when needed. 


POTASSIUM FLUORIDE, K F, and potassium hydrogen fluor- 
ide are sometimes used instead of the ammonium salt in the ana- 
lysis of silicates, borates, titanates, ete. Tests and preparation 
are similar to ammonium salt (see page 34). 


POTASSIUM HYDRATE, KOH. 


Usses. For neutralization of acids and for their titration by 
means of volumetric standard solutions, which are preferable to 
sodium hydrate on account of less liability of corrosion of burettes 
and to ammonia on account of greater stability of titre. For precipi- 
tation of insoluble metallic hydrates from the solutions of their 
salts. Some of these are soluble in excess of the reagents, as alumi- 
nium, beryllium, chromium, zinc, lead, and may, therefore, be sepa- 
ratedfromtheinsolubleones, asiron, manganese, cadmium, bismuth, 
etc. By boiling the solution chromium and beryllium are again pre- 
cipitated, but not aluminium, zinc or lead. Beryllium may thus be 
separated from aluminium, but only when the solution of KOH 
is so diluted that it contains 0.1 % of the mixed hydrates, other- 
wise the precipitate of beryllium hydrate carries with it some 
aluminium (Zimmermann). In ultimate organic analysis K OH 
serves to determine the quantity of C O2, which is absorbed either 
by solution of potassium hydrate contained in Liebig’s bulbs, or 
their modification, or by solid hydrate in suitable tubes. Also for 
making Moore’s (Heller’s) test for glucose, whose solution it colors 
brown, slowly in the cold, rapidly when heated. Also as addition 
in other glucose tests by cupric, bismuth, mercuric and other salts, 
picric acid, etc. Also for giving color reactions with some alka- 
loids by fusing them with dry K OH, grass green with quinine and 
quinidine, blue-green with cinchonine and cinchonidine, greenish- 
yellow, changing tored with cocaine (Lenz). Alsoin microscopic 
work for clearing up and corrosion of tissues, separating starch 
from the epidermis of grains in flour examinations; for coloring 
lignin yellow (woodpulp in paper); for saponification of fats, etc. 
Also for preparation of a stable solution of starch (Mueller). 
K O H = 55.979. 

Tests. Potassium hydrate is usually sold as a white, fused 
mass, often molded into thin pencils, and of different degrees of 
purity. For filling potash bulbs and tubes for absorption of C Oc 
a moderate degree of purity suffices. Neither is absolute purity 
required for volumetric solution to determine the percentage of 
acids, as the solution is standardized by normal acids, nor for de- 





POTASSIUM HYDRATE, 163 


tection of glucose, for fusion with alkaloids or for microscopic 
work. But for separation of metals, for determination of sulphur 
in organic compounds, potassium hydrate must be pure. Small 
traces of sodium hydrate are objectionable only in special cases. 


Pure potassium hydrate dissolves without residue at 15° C. in 0.47 
parts of water and in 2 parts of alcohol; in either case no deposit must 
show itself after dilution with the solvent and standing for some 
hours. After acidulation with acetic acid no precipitate must be 
produced by Hz §; nor after such acidulation and subsequent addi- 
tion of a slight excess of ammonia must any precipitation be pro- 
duced by addition of ammonium sulphide or oxalate, nor by simply 
simply heating to 100° for half an hour, with occasional replacing 
of the evaporated ammonia, and setting aside to cool. To detect 
traces of impurities, several grammes of K OH must be examined. 
After acidulation of the K OF solution with nitric acid neither 
ammonium molybdate,nor barium chloride,nor silver nitrate must 
occasion any turbidity. To detect traces of carbonate in the hy- 
drate, a solution of 15% is made and added to a mixture of 10 Ce. 
saturated solution of calcium sulphate with 5 Ce. of water; 0.2% 
of carbonate produced a decided precipitate of calcium carbonate 
(Koster). 


After acidulation with H Cl and evaporation to dryness no insol- 
uble residue must be left. After acidulation with sulphurio acid 
and addition of a few crystals of pure pyrogallol, the solution of 
potassium hydrate must not show a brown or yellow zone of con- 
tact when stratified over concentrated H2S O4 (abs. of traces of 
nitrates and nitrites). With pure aluminium or zinc it must evolve 
pure hydrogen gas, which does not stain paper moistened with sil- 
ver nitrate. After conversion into chloride it must give a pure 
potassium spectrum. 


PREPARATION. Potassium hydrate is made by decomposition 
either of carbonate by calcium hydrate, or of sulphate by barium 
hydrate, or of nitrate by metallic copper. According to the pur- 
ity of the ingredients a more or less pure product is obtained. 
Carbonate derived directly from wood-potash or from various po- 
tassium minerals is apt to contain many impurities, while that ob- 
tained from bicarbonate or from purified cream of tartar furnishes 
better results. The more impure varieties of commercial hydrate 
may be purified by solution in strong alcohol (free from aldehyde, 
fusel oil, etc.), which leaves most impurities undissolved, evapo- 
rating and fusing the dry residue. That resulting from careful 
decomposition of pure sulphate by barium hydrate is pure. So 
ig that occasionally made from pure metallic potassium, In all 


164 POTASSIUM IODATE. 


operations requiring heating (or even preservation) of potassium 
hydrate in concentrated solution or fusion, vessels of glass, porce- 
lain or platinum must be avoided and iron or, still better, silver 
used. Access of air must be avoided as much as possible, as its 
C O.is absorbed with great avidity. 

To prepare the hydrate from carbonate 2 parts of potassium car- 
bonate are dissolved in 24 parts of water, the solution heated to 
boiling and 1 part of pure, freshly-slacked lime added gradually in 
small portions, with frequent stirring and occasional replacing of 
the evaporated water. When a small portion of the filtered liquid 
no longer effervesces with acid, the mixture is covered and set 
aside to deposit the calcium carbonate; the clear liquid is then re- 
moved by decanting or by a syphon, carefully protected from the 
C Oc of the air and may be used directly as a test solution, or for 
preparing normal solution, or evaporated in a silver dish and 
fused. From potassium sulphate the hydrate is prepared by care- 
fully neutralizing a solution of 16 parts of crystals of barium hy- 
drate in 48 parts of boiling water, by adding pure potassium sul- 
phate (about9 parts) until a small filtered portion no longer gives 
a precipitate with potassium sulphate. The mixture is covered 
and set aside until the barium sulphate has subsided; it is then de- 
canted, evaporated to dryness and, if necessary, freed from a trace 
of sulphate by re-solution in strong alcohol and evaporation. 
Wehler directs heating to redness in a copper crucible 8 parts of 
fine cut metallic copper with 1 part of pure saltpetre and leaching 
out with water. 

Normal potassium hydrate is made either by using the solution 
obtained in the above processes, or dissolving a fair commercial 
hydrate, free from carbonate, and standardizing by means of nor- 
mal acid. The solution then contains 55.979 gr. of K O H in one 
litre. 

POTASSIUM HYPOCHLORITE, K Cl O, is sometimes used in- 
stead of the sodium salt as a source of chlorine; for oxidation of 
nickelous to nickelic salt; for solution of arsenic spots in Marsh’s 
test, and, instead of hypobromite, for liberation of N from urea. 
It is made by precipitating a solution of calcium hypochlorite by 
potassium carbonate. . 


POTASSIUM IODATE, KI 0s. 


Ussts. To furnish, by adding sulphuric acid, iodice acid to detect 
reducing alkaloids by liberation of iodine, e. g., to distinguish 
morphine, which rapidly reduces, from codeine. K I Os = 213.456. 

Tests. Potassium iodate crystallizes in the regular system; at — 
15° C, it dissolves in 18 parts of water; at 560° it melts and sepa- 





POTASSIUM IODIDE. 165 


rates into potassium iodide and oxygen. The residue may then be 
tested for purity as directed for potassium iodide. The commer- 
cial salt is pure enough for use. 

PREPARATION. 12.7 parts of iodine are diffused in water and 
chlorine passed into it until the iodine has completely dissolved; 
12.2 parts of potassium chlorate are then added and heat applied 
until no more chlorine escapes. On cooling, crystals of iodate 
form, which are purified by recrystallization. 


POTASSIUM IODIDE, KI. 


Usres. For detection of lead, silver, mercury, palladium, etc., 
by colored precipitates. For preparation of volumetric and other 
test solutions of iodine, of mercuric iodide, Nessler’s, Mayer’s, etc. 
For the absorption of chlorine, which liberates iodine and may 
thus be determined by solution of sodium hyposulphite. With 
starch paste as indicator of ozone, nitrous acid, chlorine, bromine, 
etc. Mixed with sulphur as a blowpipe reagent for bismuth. Also 
in 25% solution in water to extract the coloring matter of old 
bloodstains for examination by the spectroscope (Helwig). KI= 
165.576, 


Tests. Pure potassium iodide crystallizes in colorless transpa- 
rent cubes (the white porcelaiu-like crystals are generally due to 
crystallizing from alkaline solution, octohedra are formed when 
free iodineis present). At 15° C.it dissolves in 0.714 parts, at 100° 
C. in 0.48 parts of water; it is also soluble at 15° in 20 parts absolute 
alcohol. At 634°it melts, and at higher temperature is vaporized; 
at 200° it absorbs oxygen and becomes contaminated with iodate 
(Petterson). For many purposes small amounts of chloride, sulphate 
or sodium do not interfere with its use, but iodate and carbonate 
must be absent in all cases. The pure salt must not give alkaline re- 
action when laid on moist testpapers. On addition of dilute sulphuric 
acid it must not effervesce nor color a starch solution blue. 
Neither must free iodine be liberated by nascent hydrogen (zinc 
and HCl). The absence of cyanogenis shown by heating the solu- 
tion with a little ferrous sulphate, ferric chloride and potassium 
* hydrate; after acidulation no blue color must appear. The ab- 
sence of chloride is shown by digesting the well-washed precipi- 
tate formed with silver nitrate in ammonia and then acidulating 
with nitric acid, only a slight opalescence must be produced. 
- Barium chloride must give no precipitate. Flame color and spec- 
trum must be pure. The absence of metallic impurities is shown, 
asin other potassium salts. 


11 


166 POTASSIUM NITRATE. 


PREPARATION. Potassium iodide free from iodate is best ob- 
tained on the laboratory scale by Frederking’s modification of 
Baup’s process. 17 gr. of pure, fine, iron wire, in short pieces, are 
covered with 100 Cc. water, and 75.8 gr. of pure iodine, in fine 
powder, gradually added. After solution of nearly all the iron 
and filtering, 25.2 gr. of iodine are dissolved in the solution, so as 
to form Fe, Ie. Fe Is, and then pure potassium carbonate added as 
long as a precipitate of ferric hydrate falls (requiring 55 gr. of dry 
Kz C Os), the mixture is filtered, heated and, if more precipitate 
falls, filtered again, evaporated and crystallized. 

A stable solution of starch and potassium iodide is obtained by 
placing in a capacious flask 5 gr. of fine starch and 50 Ce. water. 
After thorough shaking, the adhering starch particles are washed 
down by a spritz-flask, and 25 Cc. of solution of 1 part of pure po- 
tassium hydrate in 2 parts of water added. Strong shaking will 
now produce a uniform gelatinous mass. To this 2 gr. potassium 
iodide dissolved in 500 Cc. of water are added, and the mixture 
heated to boiling with constant agitation. After cooling, the clear 
solution is diluted to one litre, and will now remain undecom- 
posed for a great length of time (Reinhardt). 


POTASSIUM NITRATE, K N Os, 


Usss. Besides its use for the preparation of potassium hydrate, 
nitrite and nitric acid, potassium nitrate serves as an oxidizer of 
carbon, of sulphides, and, especially in blowpipe work, for recog- 
nition of chromium salts by conversion into yellow potassium 
chromate; in assaying for making black, gray and white flux and 
uncombined for oxidation of the sulphides of silver, copper and 
lead. Also for making solution for standardizing indigo solution. 
In many cases sodium nitrate is now used instead of the potassium 
salt. KN Oz = 100-920. 

Tests. Potassium nitrate forms colorless, rhombic prisms, sol- 
uble at 15° C. in 4 parts, at 100° in 0.5 parts of water, nearly insol- 
uble in alcohol. The tests for metallic impurities are the same as 
for other potassium salts. The solution must not be rendered tur- 
bid by silver or barium nitrate, must show no precipitate with . 
ammonium molybdate, nor give arsenic reactions by Gutzeit’s test 
(see, on page 117, ferrous sulphide). It must be neutral to test- 
papers. With chlorine water and starch solution no iodine or bro- 
mine reaction should be given. 

PREPARATION. On asmall scale, pure potassium carbonate may 
be neutralized with pure nitric acid and crystallized. Commer- 
cial saltpetre is purified by repeated recrystallization, rejecting 
the first crystals, which contain the less soluble earthy salts, as 





POTASSIUM NITRITH. 167 


well as the mother-lye containing the more soluble chlorides. 
Thecrystals are, by stirring, obtained as small as possible, to pre- 
vent enclosure of mother-lye. Thecrystalline powder is then 
placed upon a funnel to drain, covered with filter-paper and 
moistened, first, with a saturated solution of pure nitrate, which, 
on percolating, withdraws soluble impurities, then with a little 
pure water, and, finally, dried. 


POTASSIUM NITRITE, K N Oz. 


Uses. To detect cobalt and separate it from nickel, etc., as 
Fischer’s salt (presence of calcium, strontium, barium and lead in- 
terferes); for conversion of aromatic amines into di-azo compounds 
and various color reactions based upon this process (Weselsky, 
Ehrlich). With sulphuric acid for the recognition of various 
phenols by characteristic colors (Liebermann), and of antipyrine by 
the green color of the nitroso compound. A standard solution is 
used in conjunction with starch and zine iodide for comparison 
with specimens of drinking water tested for nitrites by the colori- 
metric method, the depth of color of starch blued by the iodine lib 
erated by nitrites serving as a means of determining the quantity. 
A solution of a small quantity of potassium nitrite (or of Nz Os) in 
nitric acid is sometimes used as Plugge’s reagent to distinguish 
antifebrin (acetanilide), which is colored red, from phenacetin, 
which remains unaffected. The reaction is analogous to that pro- 
duced by mercurous nitrate with free nitrous acid (also called 
Plugge’s reagent) on phenol. K N Oz = 84.96. 

Tests. Potassium nitrite is usually sold in fused masses or pen- 
cils, very deliquescent and oftenimpure. For most purposes the 
presence of a small amount of nitrate is not objectionable, but me- | 
tallic impurities, chloride and sulphate must be absent, and may 
be detected as in other potassium salts. ; 

PREPARATION. Potassium nitrate is fused with twice its weight 
of lead, the mass being constantly stirred until the lead is oxidized. 
It is then leached out with cold water, filtered and carbonic acid 
passed into the solution to precipitate the lead. After filtering, 
nitric acid is added to neutralize any carbonate and the liquid 
evaporated. The first crystals, containing nitrate of potassium 
and lead, are rejected and from the residue small prismatic crys- 
tals of potassium nitrite are obtained. If He S should still show a 
trace of lead in these, and it is necessary to remove this, the crys- 
tals are fused for about 12 hours, to decompose the rest of the lead salt 
and render it insoluble. The residue is recrystallized and care- 
fully preserved. The standard colorimetric solution is made by de- 
composing 0.406 gr. of pure silver nitrite by a slight excess of pure 


11" 


168 POTASSIUM OXALATE—PERMANGANATH, 


potassium chloride, diluting with water to 1 litre and filtering. 
Each 1 Ce. corresponds to 0.01 milligr. of Ne Os. See also silver 
nitrite, starch and zine iodide. 


POTASSIUM NITROPRUSSIDE, Kz Fe.N O.(CN)s + 2 He O, 
is proposed as a reagent for albumin in urine (Mya). In action it 
is similar to the ferrocyanide and does not differ from that of the 
sodium salt, see sodium nitroprusside. 


POTASSIUM OXALATE. 


UsEs. The several oxalates have been used, instead of oxalic 
acid, as reducents, etc., and especially for standardizing volumetric 
‘solution of potassium permanganate, but only the 


TETROXALATE, K H C2 O4 . He C2042 Ha O, deserves notice. 
On account of its permanence in composition and great stability in 
solution it is recommended as starting point for alkalimetric and 
oxidimetric solutions (Kraut, Albricht, Meissl). Mol. W. = 258.515. 

Tests. Potassium tetroxalate (quadroxalate) crystallizes in 
transparent, monoclinic prisms, which dissolve at 18° C. in 55.25 
parts of water, more readily in boiling water, and become anhy- 
drous at 126° C. The salt is tested as directed for other potassium 
salts for absence of metallic impurities, and of nitrate, chloride and 
sulphate. 

PREPARATION. Either by mixing boiling hot solutions of 1 part 
of potassium carbonate and 2.1 parts of oxalic acid, crystallizing 
and recrystallizing in very small crystals from boiling water; or by 
purification of the commercial salt. This consists principally of a 
mixture of K HC, O1-+ H, O with K H C204. Hy Co O, + 2 H2 O. 
The amount of oxalic acid necessary to convert it into tetroxalate 
is ascertained by titration with normal potassium hydrate, and a 
slight excess of this amount is mixed with the salt in boiling solu- 
tion. On cooling the crystallization is interrupted so as to obtain 
small crystals. These are placed on a funnel to drain and are 
washed with a little very cold water to remove more soluble im- 
purities until the filtrate no longer shows impurities. If necessary, 
another recrystallization from boiling water is resorted to. The 
salt is dried at a low temperature in an exsiccator. 

Potassium ferrous oxalate, see page 117. 


POTASSIUM PERMANGANATE, K Mn O.. 


Usrs. The readiness of potassium permanganate to yield its 
oxygen makes it a valuable agent ina variety of operations in volu- 
metric analysis. With the addition of sulphuric acid it serves to 
convert oxalic acid into carbon dioxide : 2K Mn O4+ 5 He Cz O4 + 


POTASSIUM PERMANGANATE. 169 


3 HeS O4 = Ke SO4-++2Mn 8S O,+ 10 CO2+8H2 0. Theintense 
purple-red solution of permanganate being during the reaction 
converted into the almost colorless manganous sulphate, so that 
the end of the process is sharply indicated by a single drop of per- 
manganate in excess, giving a permanent rose-red color. Organic 
substances in drinking water are in similar manner determined, 
and conventionally estimated by assuming them to be five times 
the amount of the potassium permanganate used in their oxidation 
(Kubel, Woods, Mohr, etc.) Ferrous salts are in like manner con- 
verted into ferric and by various modifications of this process, 
direct or indirect, quite a variety of substances are volumetrically 
determined. It is also used for titration of spir. etheris nitrosi, 
etc. Methylalcohol reduces dilute solutions of permanganate very 
rapidly, ethyl alcohol rather slowly, so that it may serve to differ- 
entiate the alcohols (Cazeneuve and Cotton). Alsoto aid in the con- 
version of the nitrogen of organic matters into ammonium salts, 
in Kjeldahl’s and Wanklyn’s processes. Alsoas Wenzel’s reagent (1 
K Mn O, in 200 H, S O,) for alkaloids. Also with indigo as indi 
eator for titration of tannin (Loewenthal, Neubauer). Mixed with 
dilute sulphuric acid it serves to detect hydrastine by the produc- 
tion of intense blue fluorescence, which disappears by further oxi- 
dation (Lyons). Also for the purification of carbon disulphide. 
K Mn O4 = 156.765. - 

TrEsts. Potassium permanganate crystallizes in long rhombic 
prisms of dark metallic lustre, deep purple-red by transmitted 
light. Soluble in 16 parts of water at 15°, in2 parts at 100° C. When 
absolutely pure, 218.58 parts of potassium permanganate should re- 

quire 448.94 parts of oxalic acid for complete decomposition. But for 

nearly all purposes a good commercial article is sufficiently pure 
as the volumetric solution is not made by solution of a definite 
weight, but by adjusting the titre by a standard solution. When 
it is to be tested for nitrates and chlorides the solution is first de- 
composed by oxalic acid and the tests applied to the colorless 
liquid. To test for sulphate the solution is boiled with excess of 
ammonia until all the manganese is precipitated, and then the 
barium salt added to the acidulated filtrate. 

PREPARATION. Of the various processes for preparing the salt 
on a laboratory scale, free from other salts, that of Sqwibb is very 
suitable. A mixture of the purest manganese dioxide and potas- 
sium hydrate is heated almost to redness, and then a little water 
sprinkled upon it and the process of heating and sprinkling re- 
peated several times. The mass is finally leached out with boiling 
water, the crystals repeated)y purified by recrystallization, and the 
product dried and preserved in the dark, 


170 POTASSIUM ACID PYRO-ANTIMONATE, 


Volumetric solutions of various strengths are made either empiri- 
cal, so that 1 litre corresponds to 10 gr. of metallic iron, or as di- 
rected by the U.S. P., 1 gr. to be dissolved in 1,000 Ce. of water; or 
in the system, generally deci-normal, and for water analysis centi- 
normal. As 2 mol. of K Mn O,furnish the necessary oxygen for 
converting 5 mol. of Hz Cz Os into C Oe, and as oxygen is diatomic, 
one-fifth of the molecular weight or 31.353 gr. are necessary for 1 
litre of normal solution and a corresponding quantity for deci and 
centi-normal. As ordinarily made these solutions change titre 
rapidly, hence the necessity of taking the titre frequently, so as to 
make corrections for the changes. <A very stable solution may be 
made by mixing in proper proportions two solutions, one stronger 
and one weaker than required, both having been boiled and left in 
a dark place for several days to deposit precipitate. The titre is 
adjusted either by oxalic acid, potassium tetroxalate, metallic iron, 
ammonium ferrous sulphate, potassium ferrocyanide, ammonium 
sulphocyanate or vanadium pentoxide, and the solution kept in 
clean, glass-stoppered bottles, protected from light. 


POTASSIUM ACID PYRO-ANTIMONATE, Kz H, She O7 + 6 H2 Q. 


Usss. This salt, which is often, though improperly, called the 
acid met-antimonate or simply antimonate, serves to detect sodium 
salts by precipitating from their neutral or alkaline solution the 
very sparingly soluble Na, Hz She O7 + 6H, O, which to the naked 
eye appears amorphous, but under the microscope shows boat- 
shaped, quadratic octahedra and prisms, which deposit themselves 
first on the parts rubbed with a stirring rod. In aqueous solution 
the reagent decomposes slowly at ordinary temperature,more rap- 
idly by boiling, forming (gummy) ortho-antimonate: Kz He Sb2O7 + 
He O = 2 K He Sb Ou, which is much more soluble in water. This 
salt also precipitates sodium as 2 Na Hz Sb O4 4+ 8 He O, but is not 
as delicate a reagent as the unchanged pyro-salt, for the sodium 
ortho-antimonate is at first quite soluble and changes into an in- 
soluble variety only after long standing. Mol. W. = 580.428. 

Tests. The salt is usually obtained in granules, requiring for 
solution 250 parts of water at 15° C., 90 parts at 100°. Asitis only 
used in qualitative work, the only test prescribed by Fresenius is 
that the solution must not give precipitates with potassium or 
ammonium chloride, but a copious one with sodium chloride. 

PREPARATION. Antimonic acid is fused with a large excess of 
potassium hydrate, the mass dissolved in water and evaporated 
until granular masses of neutral pyro-antimonate, K4 She O7, sepa- 
rate. These are removed from the motherlye, drained and left in 
contact with about 20 parts of water for several hours, The salt 


POTASSIUM STANNOUS CHLORIDE—SULPHATE. 171 


separates into acid pyro-antimonate and caustic alkali; the gran- 
ules are drained, washed with a little water and preserved until 
needed. Brunner directs deflagrating in small portions a mix- 
ture of equal parts of tartar emetic and saltpetre fluxing the resi- 
due until it flows quietly and, after cooling, extracting the mass 
by boiling water. On cooling, the salt separates as a heavy, white 
powder. 

The solution should only be made shortly before it is needed, 
and then only with cold water. 


POTASSIUM STANNOUS CHLORIDE, Sn Cle. 2K Cl + H2 O. 


_Usrs. This double salt produces in nearly neutral solutions of 
sodium, ammonium and lithium white precipitates, and thus serves 
for their detection, especially that of sodium, in solutions in which 
only alkali salts must be present; alcohol, free acids and borates 
also interfere with the reaction; carbonates must be neutralized 
by hydrochloric acid (Hager). Mol. W. = 355.226. 

PREPARATION. Five grammes of stannous chloride in crystals 
dissolved in 10 Ce. of water and 6.5 gr. of potassium hydrate, dis- 
solved in 40 Ce. of water, are mixed, reserving a little of the potas- 
sium solution. After the mixture has stood for an hour and de- 
posited any insoluble matter, it is decanted and the rest of the po- 
tassium solution, diluted with 15 Cc., isadded. After several hours 
standing in a close vessel the solution is filtered and carefully pre- 
served. Long exposure to air might oxidize and produce stannic 
salt, by whose presence rubidium would be precipitated. 


POTASSIUM STANNOUS SULPHATE, KzS 04.SnS 04, 


Usres. For the titration of nitric acid. The reaction depends 

upon the conversion of the stannous into the stannic sulphate at 
the expense of the oxygen of the nitric acid, presence of a consid- 
erable excess of sulphuric acid being necessary. 4(K2S O4.Sn§S 
Os) + 4H2S O01 +2HN Os =4 Ke S O14 + 48n (S Oslo + N2O +5 
He9O. The solution is colored blue by diphenyl-amine and remains 
so untilthe nitric acid is completely reduced, when it becomes col- 
orless (Longt). K2S O4.Sn S O4 = 887.884. 
' PREPARATION. Stannous sulphate is first made by adding an 
excess of pure tin to hot, concentrated, pure sulphuric acid. A 
white salt results, which dissolves in 5.5 parts of water, hot or 
cold. Of this salt 11 parts are mixed with 9 parts of pure neutral 
potassium sulphate and dissolved in 65 parts of boiling water. 
The solution on cooling and after evaporation deposits silky crys- 
tals of the double salt, which are purified by recrystallizing. 


172 POTASSIUM SULPHATE. 


_ Decinormal solution containing 37.7884 gr. of the dry anhydrous 
salt, corresponding to 11.7698 gr. of metallic tin, is made by dis- 
solving 40 gr. in 800 Ce. of 50% sulphuric acid, spec. gr. 153. If 
any residue remains undissolved a minimum of conc. hydrochloric 
acid is added to dissolve it, and then the strength of the solution 
is ascertained by a deci-normal solution of potassium nitrate 
(10.092 gr. K N Ogin 1 litre) after addition of a large excess of 
sulphuric acid and a drop of solution of diphenyl-amine. From 
the ascertained strength of the stannous solution the titre is care- 
fully adjusted by dilution with dilute sulphuric acid to deci-normal 
strength, so that it runs accurately together with the deci-normal 
nitrate. Whenever a specimen of nitric acid or nitrate is to be 
tested it is after weighing, diluted and at least 3.5 volumes of sul- 
phuric acid and a drop of diphenyl-amine added before titra- 
tion with the stannous solution. 


POTASSIUM SULPHATE. 


- a. NEUTRAL POTASSIUM SULPHATE, Kz S Ou. 


Usss. To precipitate barium, strontium and lead salts by con- 
verting them into insoluble sulphates, without introducing free 
acid into the solutions. Also for preparing pure potassium hy- 
drate, potassium stannous sulphate, etc. To detect aluminium 
salts by the octahedral crystals of alum formed by mixing concen- 
trated solutions, especially used as microchemical test. Ke S Os 
= 173.882. 

Tests. Pure potassium sulphate forms colorless, rhombic 
prisms, terminating in pyramids, much resembling the hexagonal 
erystals of quartz. It is soluble in about 9.1 parts of cold and 4 
parts of boiling water, insoluble in absolute alcohol. It is tested 
for metallic impurities like other potassium salts and should give 
no acid reaction with test papers, no precipitate with silver nitrate 
or ammonium molybdate, no blue color with diphenyl-amine and 
sulphuric acid, nor leave an insoluble residue after evaporation to 
dryness with hydrochloric acid. 

PREPARATION. The commercial salt usually obtained as a bye- 
product of various operations, is liable to be contaminated with 
different impurities derived from such origin, but may be obtained 
pure enough for most purposes by careful, repeated recrystalliza- 
tion. Onasmall scale, it may be obtained by saturating pure bi- 
carbonate with pure sulphuric acid. The test solution contains 

- 1 part in 12 parts of water, 


POTASSIUM SULPHATE, 173 


b. ACID POTASSIUM SULPHATE, K HS O.. 
Potassium bt or di-sulphate. 


UsrEs. Jn conjunction with potassium permanganate for libera- 
tion and removal of bromine and its separation from chlorine 
(Berglund). Also as a flux for decomposing and rendering solu- 
ble ores and minerals insoluble in acids, emery, corundum and 
other aluminium compounds, rutile, sphene and other titanium 
minerals, chromic iron ore, etc., and for cleansing platinum cruci- 
bles. K HS O4 = 185.868. 

Tests. Potassium acid sulphate crystallizes from acid solutions 
in rhombic tables. It melts at 200° C,, and, on cooling, forms 
monoclinic crystals. At 15° C. it dissolves in 2.3 parts of water, at 
100° in 0.9. From the aqueous solution neutral sulphate crystal- 
lizes first. It is tested like the neutral sulphate, but contains 
double the amount of acid, as may be tested by titration with po- 
tassium hydrate and phenol-phthalein. 

PREPARATION. The salt is obtained as a bye-product in the 
manufacture of nitric acid from saltpetre, etc. It is made pure 
on the small scale by melting together in a platinum vessel 13 parts 
of pure neutral sulphate with 8 parts of pure cone. sulphuric acid 
and discontinuing the heat as soon as white vapors of sulphuric 
acid begin to escape, or by adding to the above ingredients 42 parts 
of water, evaporating almost to dryness and collecting the crys- 
tals, which are then recrystallized from a minimum of water, 
acidulated strongly with sulphuric acid to prevent the separation 
of neutral salt. 


POTASSIUM SULPHIDE, in the crude commercial state (hepar 
sulphuris), is used to render hydrogen sulphide free from arsenic, 
by passing the dry gas through long tubes filled with lumps of 
fused hepar and heated to 350° C. (Von der Pfordten). 


POTASSIUM SOULPHOCARBONATE, K, CS8s, is used for detec- 
tion of cobalt and nickel. Even in very dilute solution, made alka- 
line by ammonia, this reagent colors nickel orange; cobalt, wine- 
yellow (Brauwm). Also as a substitute for Hz 5S, to precipitate so- 
lutions of métals (Hager). It is prepared according to Fresenius 
by dividing 25% solution of potassium hydrate in two equal parts, 
saturating one-half with HeS, digesting the other half with about 
1-25th of its volume of carbon disulphide, and after removal of the 
surplus of C S82 mixingthe solutions. A dark orange-colored solution 
results, which must be carefully preserved, as it decomposes ra- 
pidly in contact with air into free sulphur and potassium carbon- 
ate, 


174 POTASSIUM SULPHOCYANATE. 


POTASSIUM SULPHOCYANATE, KC NS. 


Sulphocyanide, Thiocyanate or Rhodanate. 


Usss. For the detection of ferric salts, which produce with it a 
deep red color, even in great dilution; this is interfered with by 
the presence of alkaline citrates, malates, tartrates, etc. Also for 
detection of nitric and nitrous acid, which with concentrated so- 
lutions produce a blood-red color similar to iron, which gradu- 
ally fades on heating or dilution. Also to detect cupric salts, 
which, after reduction by S Oz, give a white precipitate of cuprous 
sulphocyanate. Also instead of ammonium sulphocyanate in deci- 
normal solution for titration of silver, according to Volhard. See 
page 40. KCNS = 96.998. 

Tests. Pure potassium sulphocyanate crystallizes in colorless, 
transparent, rhombic prisms, similar to saltpetre. It is very deli- 
quescent, dissolving in 0.5 parts of water at 15° C., and producing 
great cold while dissolving. Soluble in 10 parts of absolute alco- 
hol. The aqueous solution must not be precipitated by barium 
chloride; pure hydrochloric acid must not produce a red color; 
ammonium sulphide must produce color or precipitate. 

PREPARATION. A mixture of 17 parts of dry potassium carbon- 
ate, 46 parts of anhydrous potassium ferrocyanide and 82 parts of 
sulphur is, by gradual increase of heat, fused and finally heated 
to redness to destroy any hyposulphite formed. After cooling, the 
mass is leached out by boiling alcohol and purified by repeated 
crystallization from alcohol, so as to remove all impurities insolu- 
uble init. The test solution contains 1 partin 10 of water. Deci- 
normal solution contains 9.6998 gr. in 1 litre, but can not be made 
by direct weighing on account of the great deliquesence of the salt, 
but must be made stronger and then standardized by deci-normal 
silver nitrate, just as the ammonium salt, page 40. 


POTASSIUM ANTIMONOUS TARTRATE, 2 [K (Sb O) Ca Hy 
Os] + H2 O, tartar emetic, has been used in volumetric solution for 
titration of tannic acid (Gerland), but the method is not a very ac- 
curate one. Mol. W.= 663.14. The commercial salt is sufficiently 
pure when recrystallized. 

Potassium tetroxalate, see oxalate, page 168. 


QUARZ, Si Ox. 


Natural crystals of silicic acid in small fragments, sometimes 
used as material for filtering acids, or coated with platinum or 
other metals for operations at high temperature, etc, See the 
article Asbestus, page 46, 8 


RESORCIN. 175 


RESORCIN, Ce H, (O H)2. 


UsrEs. Resorcin, or meta-di-ory-benZol, is a very delicate reagent 
for iodoform, chloroform and chloral hydrate. When a small 
quantity of resorcin is dissolved in a slight excess of potassium 
hydrate solution it produces an intense red color, due to the forma- 
tion of rosolic acid, on heating it with even traces of iodoform 
(Lustgarten), of chloroform or chloral hydrate (Schwarz). The re- 
action is especially adapted to finding traces of these substancesin 
urine. Small amounts of ferric chloride may be identified by this 
reagent by producing a violet blue color. It also serves for the 
detection of saccharin, Fahlberg (ortho-sulphamine benzoic anhy- 
dride, or benzoic acid sulphinide, Ce H1. CO.S O.N H), which 
is now extensively used as a substitute for sugar; on addition of 
resorcin and a few drops of concentrated sulphuric acid toa small 
amount of saccharin and heating, the liquid assumes, in succession, 
a yellow, red and then a dark green color, while S Oz escapes with 
effervescence. If, after cessation of this effervescenve,the liquid is 
made slightly alkaline by potassium hydrate, a strong, green fluor- 
escence indicates the presence of saccharin (Jra Remsen). It is also 
used for the detection of carbohydrates (Zhi, modified by Molisch), 
especially glucose, which gives a red color when brought together 
with an alcoholic solution of resorcin and floated on cone. sulphuric 
acid. By melting resorcin with sodium hydrate phloroglucin is 
obtained. Mol. W. = 109.764. 

Tests. Resorcin forms small, colorless, rhombic prisms, melt- 
ing at 110° C.; subliming at 276.5°. It dissolves in 0.67 parts of 
water at 12.5° C., and easily in alcohol and ether. Its aqueous so- 
lution should not form a precipitate with lead acetate (abs. of py- 
rocatechin). It should sublime without residue. The commercial 
article is sufficiently pure if not browned by exposure to air and 
light. If such is the case, it must be carefully resublimed. 

PREPARATION. A somewhat impure product, difficult to purify 
completely, is obtained by melting ammoniacum, galbanum, asa- 
foetida or xanthorrhea resin with caustic alkali and extracting 
the fused mass by ether. A better product is obtained on the 
small scale by fusing potassium or calcium benzol-meta-disulpbon- 
ate with potassium hydrate, dissolving the fluxed mass in acidu- 
lated water, extracting the resorcin with ether and subliming the 
residue remaining after distilling off the ether at 276.52 C. On the 
large scale resorcin is made by adding gradually, in a thin stream 
and with a constant stirring, 24 parts of benzol to 90 parts of fuming 
sulphuric acid, contained in a cast iron still, provided with stir- 
ting apparatus and leaden condenser, After keeping up the 


176 SAFRANINE HYDROCHLORATE. 


stirring for two or three hours, the benzol disappears, the heat is 
then raised to 275° C., when a little benzol and water distill over. 
The temperature is kept up for some time and the mixture, now 
containing benzol-meta-disulphonic acid, is then poured into 2,000 
parts of water and neutralized by milk of lime. -Calcium sulphate 
precipitates and is separated, and the solution contains calcium 
benzol-meta-disulphonate. The filtrate is evaporated to dryness 
and 60 parts of the dry salt are mixed with 150 parts of caustic 
soda and very little water, and kept for eight or nine hours at a 
temperature of 270° C. The acid is thereby converted into resorcin. 
The mass is dissolved in 500 parts of boiling water, a little hydro- 
chloric acid added and boiled to expel S Oe. After cooling, the 
liquid is shaken with ether in a suitable apparatus, the ethereal 
solution is separated, the ether distilled off and the residue of resor- 
cin sublimed at 276.5° C. 


RUTHENIUM CHLORIDE is used to detect hyposulphites (thio- 
sulphates), even in traces, by assuming with them in presence of 
ammonia an intense red color, visible yet in great dilution (Carey 
Lea). Ruz Cle = 415.22. 


SAFRANINE HYDROCHLORATE, Ca Ha Ni.H Cl. 


Uses. Commercial safranine (the hydrochlorate) has been intro- 
duced by L. Crismer as a most delicate reagent for the detection 
of glucose, especially in urine, and of disaccharides and glucosides, 
after heating them with dilute acid. It is a di-azo-derivative of 
ortho-toluidine, and yields with water or alcohol red solutions 
(often used for staining tissues in microscopical work or for color- 
ing wine); the solution in presence of alkali is rendered pale yel- 
low by reducents, zinc dust, nascent hydrogen, glucose, ferrous 
salts, etc., forming a leuco-compound similar to that of indigo. 
This reduction occurs very slowly at ordinary temperature, but 
rapidly above 60° C. A solution of 1 gramme of safranine ina 
little alcohol and diluted to 1 litre with water is used for detection 
of glucose in urine. Of this 5 Cc. are used for 1 Ce. of urine, 2 Ce. 
of solution of sodium hydrate added and heat applied. The small 
trace of reducent present in normal urine (generally supposed to 
be glucose) does not suffice to reduce this amount of safranine, so 
that, if the color becomes yellow, an abnormal amount of glucose 
must be present. Shaking with air, or standing in contact with it, 
restores the color, so that for delicate testing of small amounts a 
layer of paraffin oil may be used to prevent access of air. 

Albumin decolorizes the safranine solution slowly but com- 
pletely; urates, creatinine and other normal constituents of urine 
do not affect it, neither does chloral hydrate or chloroform, 





SILVER AND ITS COMPOUNDS. 177 


Tests. The commercial article is sufficiently pure. It might be 
tested with a small amount of glucose to ascertain its efficiency. 
The brown-red crystals have, when dry, a greenish, metallic lustre, 
and are very soluble in water or alcohol. A small crystal thrown 
into concentrated sulphuric acid dissolves with a deep green color, 
which, by gradual addition of water, drop by drop, turns, first, a 
deep indigo blue, then violet and, finally, red.. 

PREPARATION. Ortho-toluidine is treated with nitrous acid, 
which affects di-azotation by uniting the nitrogen of two of the 
three amido-groups present in three toluidine molecules, so that 
-NHe+.NHe=.N:N.+2He2. The product is then oxidized 
by means of potassium dichromate. The crystals are then purified 
by recrystallization from very dilute, hot hydrochloric acid. 

Nigrosine and tnduline may be substituted for safranine and are 
similarly decolorized. 

Scheibler’s Reagent, see phospho-tungstic acid, page 18. 


SILVER AND ITS COMPOUNDS. 
SILVER, Ag. 


Usrs. Pure metallic silver is used for preparing various salts; 
for adjusting the titre of volumetric solution of sodium chloride; 
in docimastic assay for alloying with gold, in the quartation pro- 
cess. In the state of fine powder or fine wire netting for absorp- 
tion of chlorine, bromine and iodine. Also in elementary organic 
analysis in fine turning chips instead of copper turnings, to decom- 
pose the oxides of nitrogen formed during combustion. Ag= 
107.675. 

Tests. Pure silver has spec. gr. 10.57; it melts at about 1,000° C. and 
at bright white heat may be distilled; while melted it absorbs oxy- 
gen, most of which again escapes on solidifying. It is insoluble in 
hydrochloric acid, soluble in nitric and in cone. sulphuric. Its so- 
lution in nitric acid must, after precipitation with dilute hydro- 
chloric acid, yield a filtrate which, on evaporation, leaves no resi- 
due. 


PREPARATION. Coin silver or silver bullion is dissolved in nitric 
acid, the solution decanted and precipitated by dilute solution of 
pure sodium chloride, and the precipitated silver chloride is, after 
thorough washing, reduced to the metallic state, either by drying, 
fusing and digesting with pure zinc and dilute hydrochloric acid, 
or by fusing with dry sodium carbonate and borax, or by boiling 
with sodium hydrate and glucose solution. For use as an absorb- 
ent of chlorine, etc., in the analysis of organic compounds, silver, 


1%8 SILVER NiTRATR. 


in fine powder, is sometimes sprinkled over asbestus, or the asbes: 
tus is soaked in solution of silver nitrate, dried and exposed to the 
vapor of H Cl, and finally heated in a current of hydrogen to re- 
duce the chloride coating to metal. 

For preparing ABSOLUTELY PURE SILVER for determination of 
atomic weights Stas gives the following directions: Silver nitrate 
is fused to decompose any platinic nitrate present, dissolved in di- 
lute ammonia water, and, after standing for 48 hours, is filtered and 
diluted so as to contain about two per cent of silver. <A slight ex- 
cess of ammonium sulphite is added, if Cu was present, until the 
disappearance of the blue color. The solution is then heated to 
between 60° and 70° C., when all the silver is reduced to metal and 
precipitates in form of fine powder. This, after cooling, is washed 
by decantation with successive portions of ammonia water until the 
washings show absence of copper and sulphuric acid. The pow- 
der is set aside to digest for several days witha fresh portion of 
ammonia, then washed with water and dried. Itis either preserved 
as powder or fused with dry sodium carbonate and borax. 


SILVER NITRATE, Ag N Os. 


Usrs. As a group reagent for the detection and precipitation of 
inorganic acids of the second group (H Cl, H Br, HI, HCN, ete.) 
and for their separation from the acids of the third group (H N Os, 
etc.), which form soluble silver salts; as well as for the titration of 
the precipitable acids by volumetric solutions. It also serves as a 
special reagent for distinguishing, by colored precipitates, chromic 
acid (red), arsenous acid (yellow, Hume’s test), arsenic acid (red- 
brown), etc. Also by suffering reduction to metallic silver, espe- 
cially in alkaline solution, formic acid, chloroform, chloral hy- 
drate, tartaric acid, glucose, aldehydes (Tollens), ete. Also for de- 
tection of arsenetted hydrogen in Fleitmann’s, Gutzeit’s and other 
tests; the test tube in which the gas is evolved is covered with a 
cap of filter paper upon which a drop of solution of silver nitrate 
is placed. If this solution is dilute the arsenetted hydrogen at 
once reduces the silver to the metallic state and thereby produces 
a dark spot, but, if a saturated solution is used, a yellow com- 
pound, Ags As (Ag N Os)s, is formed, which is decomposed by 
water and separates black metal. Ag NOs= 169.576. 

Tests. Silver nitrate forms colorless, rhombic plates, soluble at 
15° C. in 0.5 parts of water and in 26 parts of alcohol of 95%. At 
218° it melts without decomposition and crystallizes on cooling. 
In the commercial salt silver chloride or potassium nitrate are 
sometimes found, also copper, etc. To detect the two former, 1 
part of the nitrate is dissolved in 1 part of water and 40 parts of 





SILVER NITRITE 179 


absolute alcohol added; if pure, no precipitate must fall. If the 
aqueous solution is fully precipitated by dilute hydrochloric acid, 
the filtrate must, on evaporation, leave no residue, even if a larger 
quantity of silver nitrate is thus tested. The washed precipitate 
may be dried and weighed and 1.69576 gr. of silver nitrate should 
_yield 1.48045 gr. of chloride. 

PREPARATION. Pure silver is dissolved in a slight excess of pure 
nitric acid, evaporated to dryness and fused. Of this, for ordinary 
test solution, 1 part is dissolved in 20 parts of water. For deci-nor- 
mal solution 16.9576 gr. are dissolved in 1 litre. Ifa salt ofless 
purity must be used, a stronger solution ismade and diluted to the 
standard of pure, deci-normal sodium chloride. 

Toilens’ reagent for glucose and aldehydes is made by dissolving 
1 gr. of silver nitrate in 10 gr. of ammonia water of spec. gr. 0.928 
(21% N Hs) and adding 1 gr. sodium hydrate dissolved in 10 Ce. of 
water. It must be carefully preserved in the dark, and as after 
drying it forms a dangerous explosive, it is safest to make it only 
as needed. On addition of this reagent to solutions of glucose or 
aldehyde metallic silver is reduced, generally as a mirror coating 
the test tube. 

SILVER NITRITE, Ag N Oz. 


Uszts. To adjust the titre of empirical potassium permanganate 
solution, when it is to be used for titration of nitrites, or for the 
preparation of a standard solution of potassium nitrite for colori- 
metric determination of nitrites in water. Ag N O, =153.616. 

Tests. Silver nitrite forms pale yellowish prisms, sparingly 
-soluble in cold, more easily in hot water. At 90° C. it begins 
to decompose, forming nitrate, metallic silver and nitrogen diox- 
ide. Light produces a similar effect. It is tested for impurities 
like the nitrate. 

PREPARATION. Solutions of 17 parts of silver nitrate and 10 
parts of potassium nitrite, each in a minimum of water, are mixed. 
The precipitate is washed, dried and preserved with exclusion of 
light. 


SILVER OXIDE, Age O, is sometimes used to remove chlorine 
without introducing another acid radical or disturbing neutrality. 
It is made by precipitating silver nitrate by potassium hydrate. 


SILVER SULPHATE, Age S Ou, is used for similar purposes as 
the oxide, especially for removing barium chloride from solution 
of hydrogen dioxide. It is made by dissolving silver in boiling 
conc. sulphuric acid, or precipitated by cone. sulphuric acid from 
saturated solution of silver nitrate. 


180 SOAP SOLUTION. 


SKIN POWDER is used for removal of tannin from vegetable 
extracts and determining its quantity by difference in specific 
gravity (Hammer). 


SOAP SOLUTION. 


Usrs. To ascertain the degree of hardness of water, i. e., its 
contents of lime and magnesia salts. The method, as derived by 
Clark and improved by Faisst and Knauss, depends upon the fact 
that pure water shaken with pure soap produces a copious foam, 
while in hard water the soap is converted into insoluble lime and 
magnesia compounds, and foaming will not occur until after the 
complete precipitation of these salts. The end of the reaction is the 
production of foam standing for 5 minutes. The result is ex- 
pressed in degrees of hardness, which differ in different countries. 
In Germany, 1° of hardness represents 1 part of Ca O in 100,000 of 
water; in France, 1 part of Ca C O3 in 100,000 of water; in England, 
1 part of Ca O in 70,000 of water. As the number of Cc. of soap so- 
lution used do not increase in exact proportion with the degrees of 
hardness, tables have been published by Faisst and Knauss to show 
the exact value of each reading of the burette, or the graduated in- 
strument, called the hydrotimeter. 

PREPARATION. While any good, white castile soap may be made 
to answer by standardizing its solution in methyl alcohol, it is gen- 
erally preferred to make the soap solution by the decomposition 
of lead plaster by potassium carbonate; 150 parts of lead plaster 
are melted on a water bath and thoroughly mixed with 40 parts of 
pure potassium carbonate. The mixture is extracted by strong 
alcohol, filtered and the filtrate evaporated to dryness. Of this 
potash soap 20 gr. are dissolved in 1 litre of dilute 60% methyl 
alcohol of spec. gr. 0.9213 and then adjusted by dilution with am- 
monia water, so that 45 Cc. exactly correspond to 100 Cc. of bar- 
ium chloride solution containing 0.523 gr. of Ba Cle-+- HeOin1 
litre, and will represent 12 German degrees of hardness or 12 mil- 
ligrammes of Ca O in 100 Cc. of water. To make the test 100 Ce. 
of the water specimen are put into a capacious flask and soap so- 
lution added from the burette or hydrotimeter until permanent 
foam remains after shaking. The number of Cc. is read off, and, 
as the degrees vary in value according to the hardness of the 
water, the corresponding values in German degrees are obtained 

from 


SODIUM AND ITS COMPOUNDS. 181 


FaIsstT AND KNAuss’ TABLE. 











Degrees Soap Degrees Soap Degrees Soap 

Hardness. Sclution. Hardness. Solution. | Hardness, Solution. 
bo pee 3.4. Co. Asn ea 18:9 Cc; 8.5 “== 33.3 Ce. 
Qi 64. * o:0 ee 20.8 ** 2.0 = haa. 00 ee 
ae H0 te=) ° 22.6 ** OO) = 86.7% 
20° =_ 9.4 ‘ 6.0 =a 244 * 10.05" ==" 584% 55 
m0. se 11:8 ** Gos se .26.2..°° 10:67¢== 5,400 tS 
we Meet 13.3) * ees: | 2505.5* 110-03 S408 03: 
Se. ee 16.1" {ice — Nees Binks 1D == 48.2" 
40 = 17.0 * Boe 6 13.0 > == 45.09" 


Of very hard water only 50 Cc. or even 25 Ce. are used and di- 
luted to 100 Ce. and the degrees found multiplied accordingly. 


SODIUM AND ITS COMPOUNDS. 


NOTE. As stated ina note on potassium and its compounds, on page 150. 
it is in many analytical operations immaterial whether the salts of sodium 
or of potassium with the same acid are used, due allowance being made for 
the difference in atomic weight. Hence, the descriptions of uses, tests for 
purity and preparation to a great extent apply to sodium salts, as well as 
those of potassium, afid need not be repeated. The tests for freedom from 
metallic impurities are the same for all sodium salts, and are, therefore, 
given with the metal atthe start and only referred to briefly with the in- 
dividual salts. 


SODIUM, Na. 


Uszs. Metallic sodium, on account of its great affinity for oxy- 
gen, iodine, chlorine, etc., removes them from their compounds, 
and by this and by the liberation of hydrogen it acts as a strong 
reducent and is much employed in organic work. For such pur- 
pose it is used either alone or, where a slower continuous action 
is desirable, as amalgam, with more or less excess of mercury. 
With acids it serves to convert arsenic into As Hs, and thus lead to 
its detection. It is used in the preparation of aluminum and mag- 
nesium, and for that purpose is now manufactured on a large 
seale. In connection with di-azo-benzol-sulphonic acid it serves 
to detect aldehydes, glucose, etc., by ared color (fischer and Pen- 
zold). See Sulphanilic Acid, page 20. Na = 22.998. 

Tests. Pure metallic sodium has a silvery lustre; it may be 
erystallized in regular octohedra; spec. gr. 0.972; melts at 95.6° C. 
‘To prevent its oxidation it must be preserved under a cover of 


12 


182 SODIUM ACETATE, 


petroleum naphtha or paraffin, or enclosed in an atmosphere of 
hydrogen. Perfectly dry chlorine or bromine does not affect it in 
the cold. Its solution in hydrochlyric acid must not give color or 
precipitate with HeS, nor after addition of ammonia with am- 
monium sulphide or carbonate, nor with sodium phosphate. The 
solution in H Cl must yield no ammonia vapor when heated with 
caustic lime, nor deposit a yellow precipitate on addition of sodio- 
cobaltic nitrite, even after long standing; its spectrum must show 
the D line unaccompanied by potassium or lithium lines. These 
tests must be given by all the salts of sodium when perfectly free from 
metallic impurities. 

PREPARATION. In an iron retort, with suitable condenser, an in- 
timate mixture of 30 parts of dry sodium carbonate, 18 parts of 
lampblack or fine coke powder and 5 parts of calcium carbonate, 
is heated to a bright red heat, and the distilling metal condensed 
under petroleum naphtha or melted paraffin. If necessary, it is 
purified by redistillation. 

Sodium amalgam is made by melting together, under a cover of 
paraffin, 1 part of sodium with 50 parts of mercury. The mole- 
cular proportion (46 to 200) is therein deviated from by adding more 
mercury as a diluent, to prevent too vigorous reaction. 


SODIUM ACETATE, Na C, Hs 02: + 3 H2O~ 


Usrs. For detection of alcohol as ethyl acetate by heating it 
with sodium acetate and sulphuric acid. For the precipitation of 
ferric salts as insoluble basic acetate. For the removal of 
phosphoric acid, ferric or aluminium phosphate, dissolved 
in hydrochloric acid becoming insoluble on heating with 
sodium acetate solution. It is also used as an addition to 
uranium solution in volumetric determination of phosphoric acid. 
It is also used in separating the bases of the third and fourth ana- 
lytical group (those precipitated by ammonium sulphide), ferric 
and aluminium salts being precipitated by boiling with sodium 
acetate as basic acetates, while manganese and zine salts remain in 
solution. Also to detect arsenic by the production of Kakodyl. 
Also for the preparation of pure acetic acid. A solution of 10 gr. 
of tannic acid and 10 gr. of sodium acetate in 100 Ce. of water is 
used under the name of tannin reactive forthe separation of 
basic from acid coaltar dyes. The basic colors, such as fuchsine, 
malachite green, phosphine, flavaniline, methylene blue, methyl 
violet, bismarck brown, etc., are precipitated from aqueous solu- 
tion by the addition of a small amount of the reagent and heat- 
ing, while acid colors, such as the phthaleins, rosaniline sulphonic 





SODIUM BROMATE—CARBONATR. 188 


acid, azocolors, alizarin, etc., remain unaffected (Weingaertner). 
Na Ceo Hz Oc + 8He O = 135.746. 

Tests. Sodium acetate forms colorless monoclinic crystals, 
which effloresce in dry, warm air. At 15° C. it dissolves in about 
3.5 parts of water; at 100°, in 0.5; in absolute alcohol it is insol- 
uble, but somewhat soluble in dilute, in 48 parts of 90%. At58° C. 
it melts, and at 128° it boils. Its solution must satisfy the tests 
for absence of other metals, as directed for metallic sodium. It 
should not effervesce with acids, nor be rendered turbid by bar- 
ium chloride, nor dilute solution of silver nitrate, nor should it 
give the nitric acid reactions with di-phenyl-amine or pyrogallol 
and sulphuric acid. When brought together with conc. sulphuric 
acid the dry salt should give neither color nor empyreumatic 
odor. 

PREPARATION. Pure acetic acid is accurately neutralized by 
pure sodium carbonate and crystallized. The test solution con- 
tains 1 part in 10 parts of water; it does not keep well, on account 
of mould. 


SODIUM ARSENATE, Na, H As O4 + 7 He O, is recommended 
by Vitali to identify morphine. A solution of morphine in con- 
centrated sulphuric acid, on heating with a little sodium arsenate, 
becomes first blue, then green, then, on dilution with water, 
changes to rose-red and, finally, to blue. Addition of ammonia 
in excess turns the color green. The commercial salt is sufficiently 
pure. 


SODIUM BROMATE, Na Br Os. 


Usss. Like those of potassium bromate, to liberate, in eonnec- 
tion with H Cl or other acids, iodine from iodide, bromine from 
bromide; hence, for titration of phenol, according to Koppeschaar. 
Na Br Og = 150.646. 

Tests. Sodium bromate forms shining tetrahedra, soluble at 
15° C. in 8 parts of water. The same tests are applicable to it as 
for metallic sodium and for potassium bromate. See page 152. 

PREPARATION. Hot conc. solution of sodium hydrate is satu- 
rated with bromine and the crystals, which separate on cooling 
of the evaporated solution, are purified by recrystallization. 


SODIUM CARBONATE. 
a. NEUTRAL SODIUM CARBONATE, Nag C Os + 10 H, O. 


Uses. Sodium carbonate is used for the same purposes as po- 
tassium carbonate, neutralization of acids, precipitation of me- 


12* 


184 ACID SODIUM CARBONATE. 


tallic bases, and transfer of the acids of their salts to the sodium 
for easier examination. In blowpipe analysis the anhydrous salt, 
Naz C Os, isemployed to reduce metals, to convert sulphates into 
sodium sulphide (hepar), ete. Also for fluxing silicates, titanates, 
etc., for which a mixture of 6.5 parts of potassium carbonate and 
5.3 parts of the dry sodium salt is mostly preferred on account of 
the mixture melting at a lower temperature than either salt un- 
mixed (see potassium carbonate, page 154). Also for detection of 
manganese, which fuses with NazC Oz to form blue-green man- 
- ganate. NagC Os= 105.67; Nae C O3 + 10 HeO = 285.27. 

Tests. Nae C Os + 10 Hz O crystallizes in colorless monoclinic 
prisms, which in dry air rapidly lose water and at 100° C. become 
anhydrous. The crystals dissolve in 1.6 parts of water at 159, in 
0.185 parts at 100°C. The anhydrous salt at 15° C. dissolves in 6.7 
parts, at 100°1n 2.3 parts. Inalcohol it isinsoluble. The tests for me- 
tallic impurities are those directed for metallic sodium, page 181; 
those for acids the same as for potassium carbonate, page 154. 

PREPARATION. The purest commercial dicarbonate (bicarbonate), 
such as made from kryolite, is placed into a glass funnel or per- 
colator, and small quantities of pure water are, from time to time, 
sprinkled upon it until the solution dripping from it no longer 
gives a brown red precipitate with mercuric chloride, and, after 
acidulation with nitric acid, ceases to be rendered turbid by bar- 
ium chloride and by silver nitrate. The saltis then dried and 
heated in a silver dish to a temperature of 150° C. to 180° C , soas 
to expel CO2 and HzO. A red heat must be avoided to prevent 
the formation of Na OH, which is copiously formed at 400° C. 

The test solution is made to contain 20% of the anhydrous salt. 


b. ACID SODIUM CARBONATE, Na H C Os. 
(Di or Bi-carbonate.) 


Uses. For similar purposes as the potassium salt. It is recom- 
mended by Holthof for fluxing silicates, etc.,in preference to the 
mixed carbonates of potassium and sodium, or either neutral car- 
bonate alone on account of its promptness of decomposing the 
minerals at a lower temperature. Na H C Og = 83.882. 

TEstTs. Pure sodium dicarbonate can be obtained in monoclinic 
prisms, but is usually met with in form of powder. It dissolves 
in about 10.5 parts of water at 15°C.; at higher temperature it 
loses C Og and is gradually converted into neutral carbonate. In 
addition to the tests for purity, as directed for the carbonate, it 
should, for some purposes, be free from neutral carbonate formed 
by exposure to heat, and, therefore, must not give a brown-red 





SODIUM CHLORIDE. 185 


precipitate with mercuric chloride, which indicates presence of 
NazC Os. For most purposes the product prepared from kryo- 
lite (e. g., that of the Pennsylvania Salt Co., at Natrona) is sufii- 
ciently pure. 

PREPARATION. Commercial dicarbonate is purified by packing 
into a percolator and washing repeatedly with small portions of 
pure water until the drippings no longer produce a brown-red 
precipitate with mercuric chloride, nor after acidulation by nitric 
acid are rendered turbid by silver nitrate or barium chloride. It 
is then very carefully dried at a low temperature. 


SODIUM CHLORIDE, Na Cl. 


Usses. For the precipitation of lead, silver and mercurous salts. 
In volumetric solution for the wet assay of silver and as compan- 
ion solution to silver nitrate in various precipitation analyses. In 
conc. solution as a precipitant of bebeerine (Bachmeyer). As a 
precipitant of albumen in urine, Roberts reeommends a solution 
of one part Na Clin 2.5 parts of water containing 5% of hydro- 
ehloric acid of spec. gr. 1.052. In the so-called halimetric method 
of analysis of beer it serves to determine the C Oz expelled by 
shaking the beer with sodium chloride by the difference in weight 
before and after the operation. It also serves for preparation of 
hydrochloric acid and chlorine and for furnishing monochromatic 
light for the polariscope. Na Cl = 58.368. 

Tests. Sodium chloride crystallizes in transparent, colorless 
cubes, soluble at 14° C. in 2.79 parts of water, at 100° in 2.52 parts; 
very sparingly in alcohol. At772° C.it melts, and if it then comes 
in contact with the flame it loses Cl and becomes partly converted 
into carbonate; hence, great care must be observed in its fusion. 
It reacts neutral to testpaper, and when pure is not deliquescent. 
It should stand the same tests for absence of other metals as are 
directed for metallic sodium, page 181. With silver nitrate it 
should yield a pure white precipitate, soluble without residue in 
dilute ammonia water. After addition of chlorine water, or di- 
lute nitrous acid, it should give no color either to starch or to 
chloroform or ether shaken with it. After heating to dryness 
with hydrochloric acid, the residue must completely dissolve in 
water. No precipitate must be produced by barium chloride. 
The colorless transparent cubes of natural rock salt (sal gemme) 
are often found absolutely pure. 

PREPARATION. When pure sal gemme is not obtainable, the 
best commercial salt may be purified by the method of Marguer. 
itte. Saturated solution of Na Clin water is charged with H Cl 
' gas, which causes the salt to separate in small crystals, which are 


186 SODIUM DIBORATE, 


drained upon a funnel, washed with hydrochloric acid and then 
heated to expel the excess of acid. 

Deci-normal solution contains 5.8368 gr. in 1 litre of water. It is 
either made by direct weighing of pure fused salt or by diluting a 
stronger solution so as to correspond with a solution containing in 
1 litre 10.7675 of pure silver converted into nitrate. Potassium 
chromate generally serves as indicator. 


SODIUM DIBORATE, Naz Bs O7 + 10 He O. 


Borax. 


Uses. Both the crystals, Nae Bs O7 + 10 He O, and the fused an 
hydrous Na, Bs O7, the so-called borax glass are used. In blow- 
pipe work it serves to convert metallic compounds into borates, 
which dissolve in the fusing borax glass and are recognized by the 
color communicated to the bead and their behaviorin different 
parts of the flame. For this purpose a small portion is fastened 
to a loop of platinum wire and heated in the oxidation flame until 
it melts into a colorless transparent globule of suitable size. To 
this while hot the specimen to be examined is attached and again 
placed into the flame for fusion. If powdered borax be mixed 
with glycerin and introduced into the flame the green color of 
boracie acid will flash up for an instant and thus detect both 
glycerin and borax. The alkaline reaction of borax is changed to 
acid by addition of poly-atomic alcohols (Klein, Jehn). In doci- 
mastic assaying borax is used as a flux to exclude air as well as to 
dissolve silica and other substances. Naz Bs O7 = 201.48; Na, Ba 
O7; + 10 He O = 381.08. 

Tests. The crystals of borax with 10 mol. of water are mono- 
clinic prisms, soluble in 14 parts of water at 15°, in 0.5 parts at 
100°. There are also hexagonal crystals, with 5 mol. of water, 
which separate from hot concentrated solution. When heated 
water escapes, puffing up the salt to a white, spongy mass, which 
at 561° C. melts to transparent, colorless buraz glass. A good re- 
crystallized article of commercial borax is sufficiently pure. Its 
solution should give no precipitate with sodium carbonate, nor, 
after acidulating with nitric acid, become turbid by the addition 
of silver nitrate or barium chloride. 

PREPARATION. The commercial salt is repeatedly recrystal- 
lized and either preserved in crystals or powder, cr it is fused in a 
platinum vessel and powdered, 





SODIUM HYDRATE—HYPOCHLORITE AND HYPOBROMITE SOLUTION. 187 


SODIUM HYDRATE, NaC H. 

Users. For the same purposes as potassium hydrate, see page 
162, for which it may be substituted in all cases where the introduc. 
tion of sodium is not objectionable. For volumetric work sodium 
is less desirable than potassium hydrate on account of its trouble- 
some foaming and greater liability to corrode glass) Na OH= 
89.958. 

Tests. For metallic impurities the same as for metallic sodium, 
page 181; for other impurities the same as for potassium hydrate 
page 162. It is soluble at 15° in 1.7 parts, at 100° in 0.67 parts of 
water, and quite soluble in alcohol. Exposed to air it first at- 


tracts moisture and then C O, and becomes covered with a crust 
of carbonate. 


PREPARATION. From sodium carbonate and calcium hydrate or 
from sodium sulphate and barium hydrate, or from metallic 
sodium, in the same manner as directed for potassium hydrate. 


Ordinary test solution contains from 10 to 12%; normal solution, 
39.958 grammes in 1 litre. 


SODIUM HYPOCHLORITE SOLUTION, Na ClO. 

Usrs. As a source of chlorine; for oxidation of nickelous to 
nickelic salts, etc.; for solution of arsenic spots in Marsh’s test, 
and their distinction from antimony spots, which do not dissolve. 
For liberation of nitrogen from urea instead of sodium hypobro- 
mite. For detection of aniline, with which it produces a violet- 
purple color; codeine dissolved in conc. sulphuric acid gives a 
blue, aesculin a violet eolor with sodium hypochlorite (Raby); 
morphine, dissolved in it and then neutralized with ammonia, 
assumes a dark red color (Fairthorne). The liquor sode chlorate 
of the U.S. P. is sufficiently pure. 

PREPARATION. 80 parts of bleaching powder (impure calcium 
hypochlorite) are diffused in 400 parts of water, and into this are 
poured 100 parts of sodium carbonate dissolved in 400 parts of 
boiling water. After cooling, enough water is added to make 1,000 
parts. Strain and preserve the clear liquid in well stopped bottles. 

- SODIUM HYPOBROMITE SOLUTION, Na Br O. 

Usses. For the determination of ammonia and urea by the 
method of Knop and Huefner. A freshly prepared solution of 
hypobromite is added to the ammonia or urea in a suitable appa- 
ratus, which permits the measuring of the nitrogen liberated by 
the decomposition: 

2NH3;+3NaBrO=38 NaBr+3H20+Ng; 

C O(N Hp +3 Na Br O= 3 Na Br+2 Hs O + C O2 + Na. 
1 gr. urea contains 0.46666 gr. N,which at a pressure of 760 Mm and 


188 SODIUM HYPOBROMITE SOLUTION. 


0° C. occupies 872.7 Ce., so that each 1 Ce. of nitrogen corr esponds 
to 0.002681 gr. of urea. Ora volumetric solution of hypobromite 
is added in excess to the urea and the surplus after decomposition 
is measured back (Hamburger). As it requires 3 mol. of hypobro- 
mite (Na Br. O = 118.726) to decompose 1 mol. of urea(C ON, H, 
— 59.976), each 1 gr. of bromine used corresponds to 0.218 gr. of 
urea. a=xx—{jw 

Sodium hypobromite also serves for ap- 
proximate determination of olefines iu min- 
eral oils). When a measured quantity of 
volumetric solution of hypobromite is added 
in excess to a mineral oil the olefines com- 
bine with the bromine, while the paraffins do 
not. The residue of hypobromite, whose Br 
has not combined, is measured back by lib- 
eration ofiodine from KI and titration with 
sodium hyposulphite (Allen). Na Br O = 
118.726. 

PREPARATION. The solution, as originally | 
directed by Knop, is made by dissolving 100 
gr. Na O H in 250 Ce. of water, and, after 
cooling, adding 25 Cc. of bromine. Other 
proportions are also used, but in all of them 
itis neceseary to have a sufficient surplus of 
Na O H to absorb the liberated C Os. 

For measuring the nitrogen many kinds of 
appaatus have been devised; among them a 
very simple but efficient one by Squibb is 
here illustrated. 

A 50 Ce. pipette (D) graduated into tenths 
is held by perforated corks (F, G)in position 
easily changed by sliding in a cylinder (E) 
filled with water or dilute sodium hydrate. 
The upper 
tube of the 
pipetteis bent 
and by means 
of along rub- 
ber tube (C) 
connects with 
the bottle (A) 
containing the 
hypo bromite 
and in a sepa- | , 
rate tube (B) i if 
4 Cc. of urine. 































































SODIUM HYDROSULPHITE—HYPOSULPHITE. 189 


Allen’s volumetric solution for olefines contains 40 Ce. of bro- 
mine and sufficient sodium hydrate to make the solution feebly 
alkaline ini litre. Its titre is ascertained by the iodine liberated 
from K I, measured by deci-normal sodium hyposulphite. 


SODIUM HYDROSULPHITE SOLUTION, Naz Se 02, 


Is recommended by Schuetzenberger and Risler (under the title 
hyposulphite) for the titration of oxygen in water, sodium sulph- 
indigotate serving as indicator. 

The solution is prepared by shaking asolution of sodium acid sul- 
phite of spec. gr. 1.25 with a surplus of zinc dust, diluting with 10 
parts of water from which the air has been expelled by boiling, add- 
ing milk of lime to alkaline reaction and drawing off the clear liquid 
without permitting access of air (Tiemann and Preusse). The 
titre is adjusted by an ammoniacal solution of 4.469 gr. of cupric 
sulphate in ilitre. 10 Cc. of this solution correspond to 0.001484 
gr. of Cuz O, equal to a loss by reduction of 1 Cc. oxygen at 0° 
and %60 Mn. barometric pressure. A measured quantity of the 
water to be examined is added to sodium sulphindigotate, which 
by addition of sodium hydrosulphite has just been deprived of its 
blue color. Shaking with the oxygen of the water restores the 
blue color, which is again dispersed by titration with the hydro- 
sulphite, and thus the contents of oxygen determined. In alka- 
line solution it serves to detect anthraquinone by aredcolor. It 
is to be regretted that the name hyposulphite, properly belonging 
to the salt Naz Se Os, has been applied to the hydrosulphite, Naz Se 
Oz, while Naz S2 Os is now often called thiosulphate, thus giving 
rise to mistakes. 


SODIUM HYPOSULPHITE, Naz Sz Os + 5 H2 0. 
Sodium Thiosulphate. 


Usss. In deci-normal solution as a companion to iodine in the 
various operations of iodimetry; for titration of free iodine and of 
all substances capable of liberating it from potassium iodide; for 
solution of silver salts; in blow-pipe analysis for detection of cyan- 
ides. A bead of hyposulphite is charged with the supposed cyanide, 
and, while hot, dipped into dilute solution of ferric chloride. A 
red color, due to the formation of ferricsulphocyanide, reveals the 
presence of cyanide (froehde). Naz Se Os + 5 He O = 247.644. 

Tests. Sodium hyposulphite crystallizes in colorless, transpar- 
ent monoclinic prisms, soluble at 15° in 0.65 parts of water, insol- 
uble in alcohol. At 56° C.it melts and at 100° becomes anhydrous, 
at 225° it is decomposed, The same tests for metallic impurities 


190 SODIUM IODATE—NITRATE. 


apply as directed for metallic sodium; but an absolutely pure salt 
israrely needed. It should not effervesce with acetic acid; 21% 
solution should not be rendered turbid by barium chloride; no red 
color should be communicated to phenolphthalein. ‘To show ab- 
sence of chlorine the salt must first be converted into sulphate, 
either by sulphuric acid or by hydrogen dioxide, the filtered solu- 
tion must not be rendered turbid by silver nitrate. Very pure salt 
is now sold by dealers in photographic goods. 


PREPARATION. The salt obtained on a large scale, as a bye-pro- 
duct of the Leblanc soda process, may be purified by repeated re- 
crystallization. Or sodium sulphite is boiled with excess of sul- 
phur, filtered and crystallized. 

Deci-normal solution contains 24.7644 gr. in 1 litre, but, on account 
of the varying amount of water in the salt, it is best prepared, not 
by direct weighing, but by adjusting a stronger solution by deci-nor- 
mal iodine (containing 12.6557 gr. in 1 litre). ‘The solution should be 
made with water from which all oxygen has been expelled by boil- 
ing and carefully preserved in the dark. 


SODIUM IODATE, Na I Os. 


Usss. This salt is occasionally used instead of potassium iodate 
to make iodic acid for alkaloid analysis. It is prepared in the 
same manner as the potassium salt, see page 164. NaI O3 = 197.435. 


SODIUM MOLYBDATE, Naz Mo O4 + 2 H2 QO, is occasionally 
used instead of molybdic acid, or ammonium molybdate, for prepa- 
ration of Froehde’s reagent, etc. It is made by saturating molyb- 
dic acid with sodium hydrate. See Molybdic Acid and derivatives, 
pp. 12 and 13 


SODIUM NITRATE, NaN 0s, 


Usss. It is used for the same purpose as the potassium salt, for 
which it is substituted when it is not desirable to introduce potas- 
sium. NaN Os = 84.899. 


Tests. Sodium nitrate crystallizes in the hexagonal system, 
forming colorless rhombohedra. At 15° C. it dissolves in 1.25 
parts of water, at 100° in 0.56 parts. It is to be tested especially 
for freedom from iodine, chlorine, sulphate and phosphate, cal- 
cium and magnesium. Tests are the same as directed for sodium 
metal and for potassium nitrate. 

PREPARATION. On the large scale, by refining Chili saltpetre 
by recrystallization; in small quantity by saturating nitric acid 
with sodium earbonate and crystallizing. 


SODIUM NITRITE—NITROPRUSSIDE. 191 


SODIUM NITRITE, NaN Oz, 


Usrs. For the same purposes as the potassium salt, except for 
the separation of cobalt, in which potassium is required; hence, it 
serves for conversion of amines into di-azo compounds, for recog- 
nition of phenols, of antipyrine, for liberation of iodine, etc. 
Also in the preparation of sodio-cobaltic nitrite, the reagent for 
potassium (Curiman), see page 75. Na N Oc = 68.939. 

Tests. The salt crystallizes in colorless rhombohedra, but is 
generally sold fused in pencils. It is very soluble in water and in 
-aleohol. The tests for purity of metallic sodium and of potassium 
nitrite apply to sodinm nitrite. 

PREPARATION. By fusion of sodium nitrate with lead in the 
same manner as the potassium salt. 


SODIUM NITROPRUSSIDE, Naz Fe (N O) Cs Ns -+ 2 H20- 


Uses. For the detection of alkaline sulphides, which, even in 
traces, give with solution of nitroprusside a red purple color, 
which rapidly changes to deep blue. Alkaline hyposulphites do 
not give the reaction while unchanged, but by heating they are 
decomposed, and the formation of sulphide is then shown by the 
above reaction. Sulphites in neutral or alkaline solution give a 
deep red with a mixture of nitroprusside and zinc sulphate (Boede- 
ker). After addition of sodium carbonate to the solution of nitro- 
prusside it serves to detect creatinine in urine by an intense red 
color, which gradually turns to straw yellow, the change being 
hastened by acidulating with acetic acid (Weyl). Acetone, under 
like treatment, becomes brown red, and on acidulation turns 
purple (Legal). Sodium nitroprusside precipitates many alka- 
loids, whose characteristic crystalline forms serve to distinguish 
them under the microscope (Davy). Itis also used in the differen- 
tiation of oils. Mol. W. = 297.785. 

Tests. Sodium nitroprusside crystallizes in ruby red, rhombic 
prisms, soluble in 2.5 parts of water at 15°, insoluble in alcohol; 
the solution is decomposed by boiling heat and by direct sunlight. 
The salt need not be absolutely pure, but must give the reaction 
with sulphides even in the minutest traces. 

PREPARATION. Four parts of powdered potassium ferrocyan- 
ide are heated with 5.5 parts of nitric acid, of spec. gr. 1.2, until 
the solution no longer gives a blue color with ferrous sulphate. 
On cooling, potassium nitrate crystallizes out and is removed; 
the solution is concentrated again and the nitrate removed on 
cooling, the last portion may be precipitated by addition of alco- 
hol. The nitroprussic acid is then saturated with sodium carbon- 


192 SODIUM OXALATE—PHOSPHATE. 


ate, the solution concentrated and the deep red crystals separated 
and purified by recrystallization. 


SODIUM OXALATE, Na Cz O4 


UsEs. In volumetric analysis of superphosphates to remove the 
calcium as insoluble oxalate and unite the phosphoric acid to 
sodium, without disturbing the relative proportions of acid and 
base (Mollenda). 

Tests. The saltis generally obtained as a crystalline powder, 
soluble in 81.3 parts of water at 15° C. and in 15.8 parts at 100°. If 
wanted perfectly pure it should give the tests directed for metallic 
sodium and for potassium oxalate; but this is hardly necessary, the 
main requirement is perfect neutrality. 

PREPARATION. A saturated hot solution of oxalic acid is accu- 
rately neutralized with sodium carbonate or hydrate, and the re- 
sulting salt carefully dried. 


SODIUM PHOSPHATE, Naz H P 0: -+ 12 Hs O. 


Uses. Secondary sodium ortho-phosphate, Naz H P Ou, is used to 
precipitate many metals, forming phosphates insoluble in water. 
After separation of the metalsof groups III, IV, V and VI by means 
of HeS and (N Ha) S, it is employed to precipitate Ba, Sr, Ca and 
Mg together, or, after Ba, Sr and Ca have been precipitated as 
carbonates, while Mg was held in solution by ammonium chloride, 
to detect and precipitate magnesium asMg N H4P O, In conjunc- 
tion with sodium acetate it serves for precipitation of chromic salts 
as chromic phosphate (Carnot), of cadmium (Carnot and Proromont), 
so as to prepare them for weighing. It is also used for precipita- 
tion of zinc in neutral solution and itsseparation from magnesium, 
which only precipitates from solution made alkaline by ammonia 
(Loeseman and Meyer). NazH P O4= 141.794; Nas H PO. + 10H, 
O = 357.314. 


Tests. Na, HP O4-+ 10 H, O crystallizesin colorless, mono- 
clinic prisms, which lose water in air. It dissolves at 15°C. in 
10.4, at 30° in 2.5, at 40° in 0.95 and at 99° in 0.611 parts of water. 
At 35° it melts, becomes anhydrous at 100°, and at 300° is converted 
into pyrophosphate, 2 Naz H P Os = Nag P2 O7 + H2 O. The solu- 
tion must not effervesce with acids, must yield no precipitate with 
ammonium carbonate, hydrate, oxalate or sulphide, the precipi- 
tates made by silver nitrate or barium chloride must completely 
redissolve on addition of nitric acid. After heating to dryness 
with H Cl no insoluble residue must be left on addition of water. 
Absence of arsenic must be shown, 


SODIUM AMMONIUM PHOSPHATE. 193 


PREPARATION. On the large scale, it is made by digesting bone 
ashes with dilute sulphuric acid, separating the calcium sulphate 
by filtering and concentration, then adding sodium carbonate to 
alkaline reaction. The filtrate is concentrated, and the crystals 
obtained on cooling are purified by recrystallization. On the 
small scale sodium carbonate is added to phosphoric acid until the 
reaction becomes alkaline and crystals obtained as above. The 
ordinary test solution contains 10% of the salt. 


SODIUM AMMONIUM PHOSPHATE, Na (N Hz) H P 01+ 4 He O. 
Microcosmic Salt. 


Ussrs. This salt is easily converted by heat into sodium meta- 
phosphate, Na P Os, and, therefore, is very useful in blowpipe 
work for detecting metals by the color of their beads, which give 
clearer and more characteristic reactions than those with borax, 
but being much more fusible require a much narrower platinum 
loop to keep them from dropping off. Silica leaves an insoluble 
skeleton of the shape of the mineral fragment containing it, and 
is, therefore, easily observed in the transparent bead. As the 
salt is not so liable to lose water of crystallization as the sodium 
phosphate, it is used for making, by direct weighing, solutions for 
standardizing uranium solution used in titration of phos- 
phoric acid. Instead of making them deci-normal (containing 
20.8657 gr. in 1 litre) an empirical solution is often employed contain- 
ing 29.339 gr. in 1 litre, corresponding to 10 gr. of phosphoric an- 
hydride, P2Os. The salt is also used for precipitation of magne- 
sium and other purposes, instead of the sodium phosphate. Na (N 
Ha) H P O4 = 186.817; Na (N Ha) H P O4 + 4 He O = 208.657. 


Tests. Microcosmic salt forms colorless, monoclinic crystals, 
soluble in about 4.5 parts of water at 15°, much more soluble in 
boiling water. The same tests fcr purity apply as for sodium 
phosphate. When heated on platinum foil or wire it must give a 
perfectly transparent mass. 


PREPARATION. Six parts of sodium phosphate and 1 part of 
ammonium chloride are dissolved in 2 parts of boiling water, and 
after a short time of heating together are set aside to cool. The 
double salt separates in crystals andis recrystallized from water 
containing a little ammonia, so as to purify them from adhering 
Na Cl. 


SODIUM PYROPHOSPHATE, Naz Pe O7-+ 10 He O, is used in 
electrolytic separations of nickel, cobalt, iron, manganese, zinc, 
cadmium, copper, silver, mercury, etc. The pyrophosphates of these 


194 SODIUM SULPHANTIMONATE, 


metals are precipitated from solution by the sodium pyrophosphate, 
add are redissolved as double salts when the sodium salt is added in 
sufficient excess. By adding either ammonium hydrate, or ecar- 
bonate, or oxalate, or various other substances, to the solution, itis 
possible to precipitate some of the metals by the electric current, 
leaving others in solution (Brand). The salt is prepared by heat- 
ing to redness pure secondary orthophosphate, dissolving and crys” 
tallizing the residue. It forms large, transparent monoclinic 
prisms, soluble in ten parts of cold and 1 part of boiling water. 
Sodium phospho-tungstate, see phospho-tungstic acid, page 18. 


SODIUM SALICYLATE, 2 Na C7 Hs Os + He O, is proposed by 
Hager as a reagent to test the purity of quinine sulphate. Toa 
saturated solution of quinine sulphate in water a few drops of 20% 
solution of sodium salicylate are added. If the quinine was pure 
the solution remains clear; cloudiness indicates presence of other 
cinchona alkaloids. It also serves todetect ethyl - and especially 
methyl - alcohol, by heating with a small amount of the salicylate 
and concentrated sulphuric acid, when it gives the odor of gaul- 
theria. See also on page 88. 


SODIUM SELENATE, Naz Se O, + 10 He O, is proposed by 
Johannson for detection of colocynthin, which is colored reddish- 
yellow in contact with a solution of sodium selenate in dilute 
sulphuric acid. Also used for demonstrating brucine in micro- 
scopical sections of strychnos seeds by using it dissolved in nitric 
acid (Lindt). The commercial product is sufficiently pure. 


SODIUM SULPHANTIMONATE, Nas Sb Sa + 9 He 0, 
Schlippe’s Salt. 


Usss. For precipitation of quinine, morphine and other alka- 
loids, as sulphantimonates of yellow to brownish color, differing 
as to formation of resinous masses, solubility in excess of precipi- 
tant, etc. Dilute aqueous solutions are used, sometimes with the 
addition of alcohol (Palm). Mol. W. = 478.525. ° 

Tests. Sodium sulphantimonate crystallizes in orange red, 
transparent, regular tetrahedra, which, by long keeping, become 
superficially coated with opaque, orange yellow Sh2Ss. The salt 
is soluble in 8 parts of water at 17°; in 4 part at 100%. Clear, 
transparent crystals are sufficiently pure for use. 

PREPARATION. 21 parts of finely powdered gray antimonous 
sulphide, Sbz Ss, 2 parts of sulphur and 380 parts of sodium hydrate 
are boiled with 180 parts of water until the gray color has disap- 
peared, filtered and concentrated. A little alcohol is then added 


SODIUM ACID SULPHATE—SULPHIDE SOLUTION—SULPHITE. 195 


and the liquid set aside to crystallize. The pure crystals are se- 
lected, washed with alcohol and then carefully preserved without 
removing the adhering alcohol. This prevents their decomposi- 
tion for a long time. 


SODIUM ACID SULPHATE, Na H S 0.4. 


Usxs. Instead of potassium disulphate as a flux for decompos- 
ing and rendering soluble aluminium minerals, such as emery, 
corundum, which are insoluble in acids, and for which the use of 
potassium salt would lead to troublesome formation of alum. (J. 
Lawrence Smith.) 

Tests. The fused mass or the anhydrous triclinic prisms are 
to be tested like the corresponding potassium salt. 

PREPARATION. 15 parts of pure crystallized sodium sulphate, 
Na, S O, + 10 H, O, and 5 parts of conc. sulphuric acid are heated 
in a platinum vessel until all of the water has escaped and white 
fumes of sulphuric acid begin to form, while the mass is in quiet 
fusion. On cooling it is broken into small pieces and preserved. 


SODIUM SULPHIDE SOLUTION, Naz S. 


Usges. In docimastic assaying for titration of zine and nickel; 
alkaline solution of lead, or alkaline solution of iron in glycerin, 
nickel chloride, or cobalt paper being used as indicators by spot- 
ting, NaeS = 77.98. 

PREPARATION. 13 gr. of sodium hydrate are dissolved in water 
to make one litre. 500 Ce. are then saturated with He S and, after 
expelling the surplus by gentle heat, are mixed with the rest of 
the solution. This now contains somewhat more than the 12.01 
-gr.of Na, S necessary to convert 10 gr. of zinc into sulphide. It 
is therefore standardized by solution of1 gr. of pure zinc, which, 
after solution in acid and neutralization by ammonia, must require 
exactly 100 Ce. of the sulphide solution. The adjusted solution is 
filled into small vials, nearly full, stopped with rubber and pre- 
served, mouth downward. 


SODIUM SULPHITE, Na, S Os + 7 Hz O. 


Uses. This salt serves occasionally as a reducent by introduc- 
ing S Og into solutions. Also for the detection of arsenic. A 
small crystal of 0.01 to 0.02 gr. of Naz S Os is thrown in a solution 
of 0.3 to 0.4 gr. of stannous chloride in 3 to 4 Ce. of pure cone. hy- 
drochloric acid and the specimen to be tested for arsenic dissolved 
in hydrochloric acid is poured upon it to form a separate layer 
above it. If arsenic be present yellow As2 83 will form above the 
line of contact, by the HeS being liberated from Naz S Os by the 


196 SODIUM TARTRATE. 


reducing power of the stannous chloride (Schlickwm). In concen- 
trated solution, to which a little pyrogallol has been added, it 
Serves to detect small traces of cupric salts by a blood red color 
(Aliame). NaeS Os = 125.86; Naz S O3 + 7 He O = 251.58. 

Tests. Sodium sulphite crystallizes in monoclinic prisms con- 
taining 7 mol. of water. It dissolves in about 2 parts of cold water; 
on heating a saturated solution anhydrous salt separates. In alco- 
hol itis insoluble. By careless keeping it changes tosulphate. For 
making the tests above stated, the only requirement is that it 
should evolve, on addition of acids, a copious amount of S Os. 

PREPARATION. A saturated solution of sodium carbonate is di- 
vided into 2 equal portions. One of them is saturated with sul- 
phur dioxide, forming acid sulphite, and then the other portion 
added and crystals obtained. 

Sodium acid sulphite is sometimes used to separate acetone, which 
forms with it a crystallized compound C3 He O. Na H S Os, from 
which acetone may be again obtained by heating with sodium 
hydrate. 

SODIUM TARTBATE. 
a. ACID SODIUM TARTRATE, NaH C4 Ha O¢ + He O. 


Uses. In freshly prepared saturated solution for precipitation 
of potassium (ammonium and calcium) as acid tartrate. Also for 
preventing the precipitation of alumina, ferric oxide, etc. Mol. 
W. = 199.614. 

Tests. The salt crystallizes in rhombic needles, very soluble in 
water. The solution rapidly spoils by fungous growths. After ig- 
nition the solution of the residue should contain pure sodium car- 
bonate. 

PREPARATION. A saturated solution of tartaric acid in hot 
water is divided into two equal parts. One-half is accurately 
neutralized by sodium carbonate, to form neutral tartrate, and the 
other half is added and crystals obtained. The solution is only 
made immediately before use, and should be very concentrated. 


b. NEUTRAL SODIUM TARTRATE, Naz C4 Ha O¢ + 2 H2 O 


UsEp for preparing Fehling’s and Nylander’s solutions, in the 
place of Rochelle salt, to aid in the solution of the metallic salts; 
the tests are the same as for the acid salt, and its properatier is 
there described. 


ce. SODIUM POTASSIUM TARTRATE, Na K C4 Hy O¢ aS 4 HeO 
Rochelle Salt. 


UsED, as the preceding, in the preparation of Fehling’s and Ny. 
lander’s solution, etc. The pure salt forms colorless, transparent, 


SODIUM TUNGSTATE. 197 


rhombic prisms, soluble in 1.7 parts of water at 6° C. After igni- 
tion its solution should only contain potassium and sodium ecar- 
bonate. The commercial salt is sufficiently pure after recrystal- 
lization. 

Sodium thiosulphate, see sodium hyposulphite, page 189. 


SODIUM TUNGSTATE. 
a. NEUTRAL TUNGSTATE, NazW 4+ 2 H20. 


b. ACID TUNGSTATE, Naio Wize On + 28 He O (= 5 Naz W Og + 
7 W Os), the ordinary commercial salt. 


Usrs. Both salts serve as precipitants of albuminoids in urine, 
also for precipitating barium from solutions of its salts in strong 
acetic acid (Ca and Mg are precipitated only from neutral and al- 
kaline solution). The salts also serve for the preparation of meta- 
tungstate and of phospho-tungstic and silico-tungstic acids, see 
page 18 and 19. 

Tests. The neutral salts form colorless, monoclinic prisms; 
the acid, triclinic. Both salts are quite soluble in water. They - 
should be free from carbonate, sulphate and chloride. A solution 
in 20 parts of water should not effervesce with strong nitric acid, 
and after boiling the mixture, the filtrate should not give a precipi- 
tate with either silver nitrate or barium nitrate. 

PREPARATION. Wolframite, a native tungstate of iron and 
manganese, is finely powdered and heated to bright redness after 
mixing with two-thirds of its weight of sodium carbonate. The 
mass is leached out by boiling water, and the hot sulution poured 
into an excess of hot cone. nitric acid. A yellow precipitate of 
W Os falls. This is separated, washed and boiled with sodium 
earbonate. From this solution the neutral salt crystallizes. By 
neutralizing a hot, concentrated solution of this salt (or, on the 
large scale, the solution of the fused mass above obtained) with 
hydrochloric acid the acid salt is prepared and obtained in crys- 
tals. 

When to the boiling, saturatedsolution of either salt some of 
the yellow W Os is added in small successive portions, so long as 
it loses its yellow color, the filtrate on evaporation yields meta. 
tungstate. 


e. SODIUM META-TUNGSTATE, Nae Ws O13+ 10 He O ( = Nag 
W Os -+ 8 W Os). 


Uses. For analysis of alkaloids, which it precipitates even in very 
small quantities, e. g., strychnine 0.0001 milligr. (Schezdler). It 
is tested as the salts above eed: 


198 STARCH—STRONTIUM CHLORIDE. 


STARCH. 


Uses. With free iodine starch forms a compound of such in- 
tense dark blue color that it remains visible even after the utmost 
dilution; bromine gives an intense yellow. Hence, starch is used 
to detect free iodine and bromine. Most varieties of starch give 
the blue color with iodine in the raw state, but a few varieties 
give a yellow or brownish color which might be mistaken for the 
bromine reaction. After boiling with water all varieties give the 
blue color with iodine, but after keeping for some time the color 
becomes uncertain again. Hence, the importance of a well keep- 
ing preparation of starch to be available at any time. Such solu- 
tions may be made by the aid of sodium, calcium or zine chloride, 
by alkaline hydrate, etc. It is also important to have permanent 
starch solutions containing soluble iodides, from which small 
traces of chlorine, bromine or nitrous acid can liberate free iodine, 
and are thus instantly detected, and measured by titration with 
sodium hyposulphite (thiosulphate). Presence of alkaline, magne. 
- sium and aluminium sulphates, of albumin, resorcin, phloroglucin 
and other organic substances interfere with the promptness of the 
starch reactions. 


PREPARATION. Starch solutions must be made thin and uni- 
form without lumps. For ordinary purposes, 1 part of starch is 
thoroughly mixed with 10 parts of cold water, and then enough 
boiling water added, with constant stirring, to make about 200 
parts of transparent jelly. To render this less liable to spoil, 
about 5% of calcium or zine chloride may be added, or sodium 
chloride to saturation. A still better keeping solution is made, 
according to Mueller, by triturating 2 gr. of starch with 25 Ce. of 
conc. alkaline hydrate solution (which converts the cellulose of the 
starch into soluble granulose) until it becomes transparent, and 
then diluting with water to one litre. The alkali must be neutral- 
ized before using. 

Soluble iodides are often added, especially K I, Zn Tz and Cd Is, - 
to the preceding solutions to the amount of 0.5 to1%. Gastine 
recommends that 5 gr. starch and 0.1 gr. of mercuric iodide be 
triturated with water, and then poured into enough boiling water 
to make one litre. The solution after filtering keeps for years. 


STRONTIUM CHLORIDE, Sr CI, + 6H, O. 


Uses. In the volumetric determination of sulphates. They are 
precipitated by strontium chloride, the resulting almost insoluble 
strontium sulphate is converted into carbonate by boiling with 


al 


STRONTIUM SULPHATE—SUGAR. 199 


sodium carbonate, and the strontium carbonate is finally decom- 
posed by a measured volume of normal hydrochloric acid and the 
surplus of acid measured back by normal alkali (Mohr). Sr Cle = 
159.114; Sr Cle+ 6 He O = 267.474. 

Tests. The salt forms hexagonal prisms, soluble at 15° C. in 
0.75 parts of water and in 24 parts of absolute alcohol. For the 
use above described, it is sufficient that its solution give no preci- 
pitate with potassium dichromate (abs. of barium). 

PREPARATION. Hydrochloric acid is saturated with strontium 
carbonate and the solution crystallized. 


STRONTIUM SULPHATE, Sr S Ou. 


Uszs. In saturated aqueous solution for the detection of barium 
by precipitation as sulphate. Strontium sulphate requires about 
3,500 parts of water for solution, and yields its acid to barium, 
which forms an insoluble sulphate. The solution is prepared by 
digesting pure, colorless, native coelestine (strontium sulphate) 
with water, or by preparing the strontium sulphate by precipitat. - 
ing its chloride or nitrate by dilute sulphuric acid, washing the 
precipitate thoroughly, and placing it in a large bottle filled with 
water, so as to obtain a saturated solution. 


SUGAR, Ci Hx On. 
Saccharose or Canesugar. 


Usss. To detect small quantities of free sulphuric acid in vine- 
gar, etc. The liquid, mixed with a small quantity of sugar, is 
evaporated in a porcelain dish on a water bath; a black or brown 
residue indicates free sulphuric acid (Runge). Also to detect bile 
acids by the deep red color they produce when mixed with sugar 
and cone. sulphuric acid (Petienkofer). A reversal of this reaction 
is used to detect free sulphuric acid in alum, aluminium sulphate, 
etc. Bile (cholic acid) is mixed with sugar and the alum added; 
red color indicates free acid (Egger). The bile reactions depend 
on the formation of furfurol by the action of concentrated acid on 
sugar (Mylius). With morphine the mixture of sugar and sul- 
phurie acid produces a violet color (Z’amba). Free arsenic acid, 
Hz As Ou, mixed with sugar solution, assumes a rose red color after 
some hours, which, by longer standing, turns to deep purple. 
Milk sugar, glucose and mannite act similar to cane sugar; arse- 
nates or arsenous acids do not give the reaction (F'resenius’ Zett- 
schrift, xxi, 124). Commercial loaf sugar is sufficiently pure. 


Wee. 


200 SULPHUR—SULPHUR TRIOXIDE. 


SULPHUR, S. 


Usss. For preparing sulphur dioxide, ferrous sulphide, sodium 
hyposulphite and other sulphur compounds. For combining with 
metals in some docimastic assays. For detection of bismuth by 
the production of the red iodide coating on charcoal, a mixture 
of sulphur and potassium iodide is added to the bismuth specimen 
and heated on charcoal before the blow pipe. S = 81.984. 

Tests. From solutions sulphur crystallizes in rhombic octo- 
hedra. It melts at 117° C., and from the state of fusion ecrystal- 
lizes in monoclinic prisms. At 447 it boils. The condensed vapor 
forms sublimed sulphur, the sulphur flowers of commerce, and 
this is the quality used as reagent for bismuth and for many 
preparations. Pure sulphur, to make pure preparations, must be 
completely volatilized by heat, must yield nothing to distilled 
water to disturb the neutrality of testpapers. It must be free 
from arsenic, which is detected by digesting with ammonia 
water, filtering and acidulating with hydrochloric acid. A yel- 
low preeipitate of Ase Oz indicates arsenic. To detect selenium 
the sulphur is heated with nitromuriatic acid, diluted with water, 
and to the clear filtrate sodium sulphite is added, when a red pre- 
cipitate indleates the presence of selenium. 


SULPHUR IODIDE. 


An impure sulphur iodide, made by melting together 2 parts of 
iodine and 8 parts of sulphur, is used in blow pipe work to produce 
on plaster of paris tablets films of various metallic iodides (Wheeler 
and Luedeking). 


SULPHUR TRIOXIDE, S Oz. 


Uses. In gas analysis, for the absorption of olefiant gas. The 
most concentrated (fuming) sulphuric acid obtainable is saturated 
with sulphur trioxide so as just to remain liquid. Into this solu- 
tion little globes of coke are dipped and introduced into the ab- 
sorption apparatus containing the dry mixture of gases (Bunsen). 
Itis also used to rapidly concentrate sulphuric acid in Kjelhahil’s 
process of nitrogen determination. Also for purposes of dehydra- 
tion. S O3 = 79.864. 

Tests. Sulphur trioxide forms long silky needles melting at 
14.8° and boiling at 46.2°. When not entirely free from H,S Osa 
compound is formed, similar to asbestus in appearance, which 
does not boil at 50° C., but which.at higher temperature decom- 
poses and gives off vapors of pure trioxide. It fumes in air and 
attracts moisture, and must therefore be carefully preserved. It 


\ 


THALLOUS NITRATE. 201 


is tested in the same way as sulphuric acid. See pages 21 and 105. 
PREPARATION. By distillation, at a gentle heat, of fuming sul- 
phuric acid, care being taken to cool the receiver weli and to pre- 
vent absolutely all excess of moisture. 
Tannin, see Tannic Acid, page 28. 
Tannin-reagent for aniline dyes, see Sodiwm Acetate, page 182. 
Testpapers, see Color Reagents, page 88. 


THALLOUS NITRATE, TIN Os, 


Uses. For quantitative determination of iodine. In very di- 
lute neutral solutions of chlorides, bromides and iodides asatu- 
rated aqueous solution of thallous nitrate precipitates theiodide 
as yellow thallous iodide, Tl I, which is totally insoluble in water 
while thallous chloride and bromide, though difficultly soluble, 
remain in solution (Huebner and Frerichs). T1 N Os = 265.616. 

Tests. Thallous nitrate forms colorless rhombic prisms, solu- 
ble at 15° C. in about 10 parts of water, much more soluble at 100°. 
At 205° it melts and at higher temperature is decomposed. It 
colors the flame green and shows a single green line in its spee- 
trum. Its neutral or acid solution should not be precipitated by 
hydrogen sulphide. Addition of ammonia water should leave the 
aqueous solution clear even after heating, and from this solution 
ammonium sulphide precipitates it as black Tl, S. After com- 
plete precipitation the filtrate on evaporation should leave no per- 
manent residue. 

PREPARATION. Metallic thallium is dissolved in dilute nitric 
acid and crystallized. 

To prepare Metrartyiic THALLIUM the flue-dust and deposit of 
the lead chambers of sulphuric acid manufactories using thalli- 
ferous pyrites is leached out by boiling water, filtered, concen- 
trated and mixed with conc. hydrochloric acid, which precipi- 
tates thallous chloride, a curdy, white salt, requiring 360 parts of 
cold water for solution, and still less soluble in hydrochloric acid. 
The precipitate is separated and added in small portions, with 
constant stirring, to half of its weight of hot conc. sulphuric acid, 
and the mixture heated to expel excess of acid. The fused acid 
sulphate resulting is dissolved in about 100 parts of water and 
H, S passed through the solution to precipitate any lead, silver, 
mercury, bismuth, arsenic, antimony or selenium, which may have 
been deriyed from the pyrites. The filtrate, after expulsion 
of the excess of H2S, is heated with ammonia water, to precipi- 
tate iron, alumina, etc., and is then concentrated to crystallize 
thallous sulphate, which separates in colorless, rhombic prisms, 


202 THYMOL—TIN AND ITS COMPOUNDS. 


From this, metallic thallium is precipitated by pure zine or by 
electrolysis, from solution made alkaline by ammonia. 


THALLIUM PAPER, made by dipping unsized paper into thal- 
lous hydrate solution, Tl O H, is used to indicate ozone, which 
turns it into brown thalliec salt ( Boetiger). The solution of thal- 
lous hydrate is prepared by adding to the solution of thallous sul- 
phate, obtained as above described, enough barium hydrate to re- 
move the sulphuric acid. The paper has also been used as an in- 
dicator for sodium sulphide titration. 


THYMOL, Ce Hs . Cs3H7. C Hs. O H. 


Usss. For the detection of glucose or other carbohydrates by 
Molisch’s method. A 15% alcoholic solution is added to the solu- 
tion to be tested. This is then floated on conc. sulphuric acid. A 
carmine red zone of contact shows the presence of glucose. Other 
carbohydrates and glacial acetic acid give similar reactions. 
Cio Hig O = 149.7. 

Trsts. Thymol forms colorless, transparent monoclinic (or 
hexagonal) prisms, melting at 50°, boiling at 222°C. They have 
the odor of thyme. At 15° it dissolves in 833 parts of water; also 
in 0.5 parts of alcohol and easily in chloroform, ether, glacial 
acetic acid, etc. The commercial article is suitable for the reac- 
tion. 

PREPARATION. From oil of thyme, monarda or ptychotis, 
which, besides thymol, Cio Hu O, contain thymene, Cio His, and 
eymol, Cio Hu. The fraction of the oil distilling above 200° C. is 
shaken with strong sodium hydrate solution, which dissolves the 
thymol and leaves the thymene, etc., to float.ontop. This is re- 
moved and from the solution in soda the thymol is precipitated 
by hydrochloric acid, and recrystallized from alcohol or from 
glacial acetic acid. 


TIN AND ITS COMPOUNDS. 
TIN, Sn. 


Uses. In blowpipe work tin is added to beads of borax or mi- 
crocosmic salt for the purpose of reducing the metallic oxides 
therein dissolved. It is also used for the precipitation of selenium 
and arsenic from their solution in strong hydrochloric acid. If 
the acid is too dilute, it may be concentrated by addition of strong 
sulphuric acid. Tinis first dissolved, forming stannous chloride, 
and this precipitates the arsenic in brown flakes, containing a 
compound of tin and arsenic (Bettendorf). Sn 117.698. 





STANNOUS CHLORIDE. 203 


Tests. Pure tin has a silvery white lustre; crystals form in the 
quadratic system; spec. gr. 7.29; the metal is very ductile and may 
be reduced to thin foil. It melts at 228.5° C. and boils at white 
heat. Heated in air it oxidizes. It dissolvesin hydrochloric acid, 
evolving hydrogen; in sulphuric acid, evolving sulphur dioxide; 
in cold, dilute nitric acid, without evolution of gas, forming stan- 
nous nitrate and ammonium nitrate; in cone. nitric acid it oxi" 
dizes to Sn Og without solution, evolving nitrous fumes. The gas 
escaping while tin dissolves in pure hydrochloric acid must not 
color paper moistened with silver nitrate, nor must the solution 
become colored by boiling with strong hydrochloric acid. This 
test of purity suffices for Betiendorf’s arsenic test. For blowpipe 
use and for preparation of pure salts, the absence of other metals 
must be shown. The solution in dilute hydrochloric acid must 
yield with HzSa pure brown precipitate, from which ammonia 
water extracts nothing soluble, but which completely dissolves in 
warm yellow ammonium sulphide. The filtrate, after precipita- 
tion with H,S, must yield neither color nor precipitate by treat- 
ment with ammonia and ammonium sulphide, nor, on evapora- 
tion, leave any permanent residue. 

PREPARATION. Small amounts of pure tin may be made by fus- 
ing pure stannous chloride with potassium cyanide. 


STANNIC CHLORIDE SOLUTION, Sn Cli, is used as an acces- 
sory in Haswell’s process of titration of mercurous chloride by 
ferric chloride and potassium permanganate. To make it, stannic 
hydrate is first prepared from stannous chloride boiled with potas- 
sium chlorate and hydrochloric acid. The solution is precipitated 
by sodium hydrate, and the washed precipitated stannic hydrate 
is dissolved in hydrochloric acid. The solution must retain for 
three hours the red color communicated by a drop of permangan- 
ate. It is also used with pyrogallic acid to detect glycerin. See 
page 19. 


STANNOUS CHLORIDE, Sn Cl, + 2 H, O. 


Usszs. For the detection of gold by formation of purple of Cas- 
sius. For reducing mercuric chloride to mercurous and finally to 
metal. For a number of reductions depending on the formation 
of stannic salt by attraction of chlorine,e. g.platinic chloride into 
deep red colored platinous chloride. For detection of brucine by 
the deep purple-red color produced in the brucine solution after 
the red color has faded into yellow. For detection of arsenic by 
the brown compound of tin and arsenic formed in solutions in 
strong hydrochloric acid (Bettendorf.) For detection of arsenic as 


204 TRI-ETHYL PHOSPHINE—TRI-METHYL AMINE. 


yellow sulphide by the joint action of stannous chloride and so- 
dium sulphite in hydrochloric acid solutions (Schlickum). See 
Sodium Sulphite, page 195. Also for the separation of caesium 
from potassium and rubidium, by removing it from a solution of 
their chlorides as a crystalline precipitate of caeswwm-stannous 
chloride, while potassium and rubidium remain in solution (Stol- 
ba). Sn Cle = 189.488; Sn Cl, + 2 He O = 225.358. 

Tests. Stannous chloride crystallizes with 2 mol. of water in 
transparent, colorless, monoclinic prisms. By cautious heating 
to 1008 the water is lost; at 250° the anhydrous salt melts, and be- 
tween 617° and 628° it boils and may be distilled without decom- 
position. It is easily soluble in water, but the solution rapidly 
absorbs oxygen and forms stannic chloride and oxychloride, un- 
less kept in contact with metallic tin. When 1 part of the dry 
salt is boiled with 5 parts of pure conc. hydrochloric acid, the so- 
lution must remain clear and colorless. The dilute solution, acidu- 
lated with hydrochloric acid, must give no precipitate with barium 
chloride. Boiling the solution with excess of sodium hydrate 
must yield no ammonia. Other tests of purity are the same as 
directed for metallic tin. 

PREPARATION. Pure tiu in foil or granules is dissolved by heat- 
ing with pure conc. hydrochloric acid, the tin being kept in excess, 
From the solution crystals may be obtained, or it may be diluted 
for use as test solution, so as to contain about 10% of the salt, 
metallic tin being kept in contact with it. 

See also Potassium Stannous Chloride on page 171. 

Stannous Sulphate, see Potassium Stannous Sulphate, page 171. 

Toluidine, see Para-Tolurdine, page 143. 


TRI-ETHYL PHOSPHINE, P (Cy, Hs)s, is used to a very limited 
extent in the analysis of illuminating gas, to absorb C Se, with 
which it forms a solid compound (Poleck). Itis a liquid of spec. 
gr. 0.812, boiling at 127.5° C., and of peculiar, narcotic odor. Itis 
made by heating phosphonium iodide, P H4 I, with three mole- 
cules of alcohol for many hours to 180° C. in s sealed tube. The 
resulting tri-ethyl phosphonium iodide, P (C, Hs)s3 H 1, is decom- 
posed by potassium hydrate into K I and triethylphosphine. 


TRI-METHYL AMINE, N (C Hs3)s, has been proposed by Vignon 
to use instead of potassium hydrate to separate ferric hydrate, 
which is insoluble, from aluminium and chromium hydrates, 
which are soluble init. The liquid is obtained as a bye-product 
of the manufacture of sugar from beets; it boils at 9.3° C., and is 
very soluble in water; it is characterized by a peculiar odor of 
herring pickle. 


TRI-NITRO-PHENOL—URANIUM COMPOUNDS. 205 


TRI-NITRO-PHENOL, Ce H, (N O2)s O H. 
(See Prcric Acid, page 18.) 


Uses. Symmetric tri-nitro-phenol is usually called picrie acid. 
In addition to the uses already enumerated (to precipitate albu- 
men and alkaloids, and to detect glucose by the intense red color 
produced by the reduction, when heated with it in alkaline solu- 
tion, of the picric to the picramic acid) it also serves to detect crea- 
tinine. A dilute aqueous solution of picric acid in dilute solution 
of sodium hydrate added to urine, or other solution of creatinine, 
produces quickly, 7m the cold, an intense red color, which, by ex- 
cess of alkali, or by addition of acetic. or hydrochloric acid, is 
changed to yellow. With acetone only a faint reddish-yellow 
color is given; with creatine a pure yellow, passing gradually into 
red; with glucose the deep red color is only produced by heating 
or by long standing in the cold (Jaffe). 

Turmeric, see Color Reagents and Indicators, page 89. 


URANIUM COMPOUNDS. 


URANIUM ACETATE, Ur 02 (C. Hs 0,). + 2H, O. 
(Uranyl Acetate.) 


Usss. Uranyl acetate precipitates phosphoric acid as acid 
uranyl phosphate, Ur O, .H P O4+ 4H, O, which is insoluble in 
water and in acetic acid and forms a most eligible compound for 
gravimetric determination of phosphoric acid (Knop). It is also 
used volumetrically, according to Pincus, in empirical solution, 
made by standardizing with solution of sodium ammonium phos- 
phate, so that1 litre of the uranium solution corresponds to 5 gr. 
P, Os. The end of the reaction is indicated by ‘‘spotting” with 
potassium ferrocyanide, which gives a brown-red color with the 
least excess of uranium solution. In the same manner it is also 
used for titration of arsenic acid (Boedeker). It has been intro- 
duced into microchemical work by Streng for the detection of | 
small amounts of sodium, based upon the formation of a double 
salt, Ur O2 (Cz Hs O,)2 . Na C, Hs O2, which contains only 6.6% of 
Na and crystallizes in regular tetrahedra, easily distinguished 
from the rhombie or quadratic forms of the uranium acetate, 
which polarize light, while the tetrahedra do not. Addition of 
magnesium acetate forms a characteristic uranium-magnesium. 
sodium acetate, crystallizing in rhombic plates, which contains 
only 1.48% of Na. Uranium acetate is proposed by Johanson for 


206 URANIUM NITRATE—UREA. 


determination of the age of beer, as it gives increasing amounts of 
precipitate with increasing age up to a certaintime. Itis also 
used for precipitation of albumin (Kowalewsky). Ur O2 (C2 Hg Oo) 
+ 2 He O = 424.058. 

Tests. Uranium acetate crystallizes above 10° C. in yellow, 
rhombic prisms with 2 He O; below 10° C. it forms quadratic 
octohedra with 3 HzO. Both forms are easily soluble in water and 
inalcohol. The acidulated solution must give neither color or 
precipitate with H, S. With a mixture of ammonium carbonate 
and sulphide no precipitate must form, while the sulphide alone 
gives a brown precipitate. The filtrate from the latter must leave, 
on evaporation, no permanent residue. The commercial salt is 
sufficiently pure for volumetric work. 

PREPARATION. Uranium pitch-blende, the most common ura- 
nium ore, containing Urs Os, is powdered and dissolved in nitric 
acid. From the filtered solution yellow fluorescent crystalline 
needles of Ur O2(N Oz), + 3 He O are obtained. To remove for. 
eign metals, if any, H, S is passed through the acidulated solution 
and the precipitate removed. The filtrate is then precipitated 
by ammonium hydrate and sulphide, the washed precipitate is di- 
gested with ammonium carbonate solution, which dissolves the 
uranium, leaving the other metals behind. The filrate is evapo- 
rated to dryness, heated with a slight excess of sulphuric acid 
and finally decomposed by barium acetate and the filtrate crystal- 
lized. The solutions are stable, if protected from light. 


URANIUM NITRATE, Ur O2 (N Os)2 + 6 He 0. 


Uses. For the same purposes as the acetate. In titration of 
phosphoric acid the formation of free nitric acid, which would in- 
terfere, is prevented by addition of sodium acetate. 

Txrsts. From watery solutions uranium nitrate crystallizes with 
6H, Oin greenish-yellow, rhombic prisms; from solutions con- 
taining much free nitrio acid it crystallizes with 3 H, O in yellow, 
fluorescent needles. The tests for purity and preparation are the 
same as directed for the acetate. Addition of alcohol and exclu- 
sion of light make its solution quite stable. 


UREA, C O(N Ha)o. 


Is occasionally used to detect furfurol by the violet color 
and peculiar absorption spectrum it produces with it on addition 
of a little hydrochloric acid (Schiff.) Also for the gasométric 
determination of nitrites. When excess of urea, a nitrite and 
dilute sulphuric acid are heated in a _ suitable apparatus 
double as much nitrogen is liberated as the nitrate con- 


WATER. 207 


tains: 2 C O (N Hz)q + N2Os=2Ne + C Oo+ (N Haz C Os. By 
reversing the process and using an excess of the nitrite, the nitro- 
gen serves as the measure of the urea decomposed (Vivier). 
CO (N Hae), = 59.976. 

A small quantity of urea may be prepared by saturating conc. 
ammonia water with carbon oxysulphide (prepared from potas- 
sium sulphocyanate and sulphuric acid). The solution is shaken 
with white lead, filtered, the rest of the lead removed by H, 8, 
and, on evaporating the filtrate, urea crystallizes in quadratic 
prisms. 


VANILLIN, Cz Hs Os, see on page 90, Color Reagents and Indi- 
cators, where the formula is erroneously given Cg Hie Os, instead 
of Cs Hs Os. 


WATER, H: O. 


UsEs. Pure water is employed as a general solvent and diluent; 
also for precipitation of substances insoluble in water from alco- 
hol, acids and other solvents, e. g., cuprous chloride from hydro- 
chloric acid, etc., and for decomposition of some metallic salts, 
e. g., bismuth nitrate into subnitrate, antimonic chloride into oxy- 
chloride, etc. Also for the formation of hydrates from anhy- 
dric oxides, calcium, barium, etc. HzO = 17.96. 

Tests. Pure water must be without color, taste or odor; must 
not change the color of testpapers; its freedom from solids in so- 
lution is shown by evaporating in a bright platinum capsule seve- 
ral Ce., which must not leave a trace of residue. Its freedom from 
such gases as can be expelled by heat must be insured by boiling 
immediately before use, that from others which may be absorbed 
from the atmosphere of the laboratory by its not giving precipi- 
tates with silver nitrate, potassium-mercuric iodide, barium hy- 
drate, or color with starch, iodide of potassium and acid. After 
protracted standing in direct sunlight with silver nitrate it must 
not blacken it. 


PREPARATION. From the purest obtainable natural water by 
distillation from any kind of still in which the condensing part 
consists of pure block tin, glass being objectionable on account of 
its yielding both alkali and silica to the condensing steam. The 
first and last fifths are to be rejected and only the middle three- 
fifths preserved in well-closed bottles of insoluble glass, safe from 
contact with absorbable gases or contamination by impure corks, 


208 XYLIDINE—ZINC AND ITS COMPOUNDS. 


Wurster’s papers, see pages 48 and 90. 
XYLIDINE, Ce Hs. (C Hs)2. N He. 


Strips of paper dipped into a mixture of equal volumes of ortho- 
cylidine and glacial acetic acid and dried are used by Schiff as a 
most delicate reagent for furfurol, the least traces of which give 
to the paper a red color. As furfuro] is among the products of 
dry distillation of carbohydrates, etc., the test may be extended 
tothem. The commercial article is sufficiently pure. 


YEAST is sometimes used for the detection and determination 
of glucose in urine bythe fermentation test. A fresh wine or 
beer yeast should be selected and thoroughly washed before use. 
The amount of glucose may either be determined by measuring 
the C Oc evolved in a fermentation tube or by ascertaining the 
loss of weight in a Fresenius & Will or a Geissler apparatus. 
The determination by difference of specific gravity, on account of 
the alcohol formed, is not very reliable. 


ZINC AND ITS COMPOUNDS. 


ZINC, Zn. 


Usrs. Metallic zinc in the form of thin sheet, granules, dust 
or in the irregular, spongy form, cast so as to present much sur- 
face, is used to substitute for other metals in their salts and thus 
to precipitate them in the metallic state; or as a reducent either 
at high temperatures or by means of the nascent hydrogen pro- 
duced when it is placed in contact with dilute acids or solution of 
caustic alkalies. Thus it serves to precipitate silver, mercury, 
lead, copper, antimony, tin, etc. It reduces in acid solutions ferric 
to ferrous salts, sulphurous acid to hydrosulphurous, He S Oz, and 
to He $8, phosphorous acid to P Hs, ete. By the aid of acids or al- 
kaline hydrates it serves to liberate H, Sb Hs, As Hs, He S, and 
thus serves especially for detection of arsenic and antimony. In 
alkaline solution, especially when in fine powder and aided by 
iron, it serves to convert nitrates to nitrites and to ammonia; in 
acid solution it is used to detect picric acid by producing a blue, 
di-nitro-cressol by a red color, etc. Zn = 64.905. (According to 
some recent investigators Zn = 65.3.) ~ 

Tests. Pure zinc has a blueish lustre, crystalline fracture, and 
may be obtained in hexagonal pyramids (when containing copper 
in regular cubes). Spec. gr. = 7 to 7.2. It melts at 412° and boils 
at 940° C. It is easily soluble in dilute acids, also in potassium, . 


ZINC, 209 


sodium and ammonium hydrate, in most cases evolving free hy- 
drogen. The principal impurities are arsenic, cadmium, lead, 
iron and copper. Not all of them interfere with every reaction, 
so that the testing for purity need only be carried out in the spe- 
cial direction needed. Arsenic is detected by dissolving a piece 
of the zinc in pure, dilute sulphuric acid, of 8.3%, in along test 
tube, covered with a cap of filter paper, moistened with a drop of: 
saturated silver nitrate solution. If arsenic be present, a yellow 
compound, Ags As (Ag N Os)s, will form (in case of traces only 
after some time). This slowly blackens, or, in contact with water, 
at once decomposes, leaving black metallic silver ( @utzeit’s arsenic 
test). Immediate blackening indicates presence of antimony, sul- 
phur or phosphorus. The solution in the test tube should be free 
from black flocculi of undissolved lead. The filtrate, acidulated, 
if not already acid, should give no precipitate by passing He S to 
saturation; after filtering and neutralizing by ammonia, ammo- 
nium sulphide should give a pure white precipitate, and the fil- 
trate from this should leave no residue on evaporation and igni- 
tion on platinum foil. A drop or two of deci-normal permanga- 
nate solution added to the solution of zinc in sulphuric acid must 
give it a permanent red color, if no iron is present. 


PREPARATION. Very few specimens of commercial zinc are 
strictly pure, and even some sold as strictly pure will not stand 
Gutzeit’s arsenic test, and can not be used in forensic analysis; 
some analytical operations, however, permit the use of zinc of less 
purity, and require only absence of certain impurities to which 
testing and purification must be specially directed. 


To obtain zinc free from arsenic, various processes may be chosen. 


. Selmi directs to stir ammonium chloride into the fusing metal, 
which removes the arsenic as volatile As Cls. 


L’ Hote uses 1 to 1.5% of magnesium chloride, which from the 
melted zinc removes arsenic and antimony, but leaves Mg. 


Stolba forms at the end of a wooden rod little balls of sulphur 
and plaster of paris; when the melted metal is stirred with the 
ball, sulphur and water vapor are evolved and agitate the fused 
mass. When no more vapors escape the ball is withdrawn and 
the scum scraped off, and the remaining metal is now freed from 
arsenic, ironand lead. If necessary, the process is repeated. 


To obtain zine absolutely pure, it must be carefully distilled 
from a clay retort, changing the receiver after the first portion, 
containing the arsenic and cadmium, has passed over. The distil- 
lation is interrupted before the whole of the metal has passed, 


210 ZINC CHLORIDE. 


Lead and iron remain inthe retort. If the product is not abso- 
lutely pure, it must be redistilled. 

Zine amalgam, made by heating 1 part of zine with 3 parts of 
mercury, is sometimes used to convert potassium iodate into 
iodide, so as to be used in starch solution for showing presence of 
chlorine, etc. (Morse and Burton). 


ZINC CHLORIDE, Zn Cle. 


Uses. A boiling saturated aqueous solution of zine chloride 
rapidly dissolves silk, while it does not affect wool or cotton; 
hence, it is employed for examination of textile fabrics (Re- 
mont). A solution of 1 part in 30 of water is used as reagent for 
glucosides, alkaloids, etc., by evaporating the specimens with it 
to dryness. Strychnine and veratrine give red color; narceine, 
olive green; thebaine, berberine and quinine, yellow; salicin be- 
comes red-violet; santonin, blue-violet; cubebin, crimson; digi- 
talin, chestnut-brown (Czumpelitz). Added to the glucose solu- 
tion towards the end of Fehling’s titration, it promotes the sepa- 
ration of CueO, and thus facilitates the observation of the end 
point (Beckmann). A solution of 50 parts of zine chloride and 16 
parts of potassium iodide, dissolved in 17 parts of water, and then 
saturated with iodine, converts cellulose into starch and reveals 
its presence by the deep blue color; hence, it is especially useful 
in microscopical work on vegetable structures. (Schulze.) With 
creatinine it forms a compound easily recognized under the mi- 
croscope by the peculiar rosette shape of its crystals. A satu- 
rated solution of Zn Cle in water boils at 300° C., and is used occa- 
sionally as a bath for maintaining that temperature. Zn Cl,= 
136.645. 

Tests. Anhydrous zine chloride forms a white deliquescent 
mass, boiling between 676° and 683°, and may be distilled without 
decomposition. In water and in alcohol it readily dissolves. 
From aqueous solution acidulated with H Cl octohedral crystals 
of Zn Cle + H2O may be obtained, but without surplus of acid the 
solution cannot be evaporated without decomposition and forma- 
tion of oxychloride, which, however, rarely interferes in the re- 
actions. The tests for purity are the same as directed for the 
metal. 

PREPARATION. Anhydrous zine chloride (which is rarely needed) 
may be made by heating zinc in chlorine gas, or by distilling the 
commercial salt, which yields Zn Cle, leaving Zn O as a residue. 
For most purposes a solution is required, which is made by satu- 
rating pure hydrochloric acid with pure zine. 


ZINC IODIDE—SULPHATER. 211 


ZINC IODIDE, Zn lo. 


Usrs. Zine iodide added to starch solution serves for detec- 
tion and as indicator in the titration of chlorine, bromine, ni- 
trous acid, etc., which render the starch blue through liberation 
ofiodine. With hydrogen dioxide it produces the same result 
(Schoenbein); in acid solutions a little cupric sulphate and ferrous 
sulphate must be added to render the reaction sensitive (7raube). 
With potassium iodide zinc iodide forms a double salt, which is 
used to precipitate alkaloids and serves especially for detection 
of narceine, whose precipitate gradually forms hair-like crystals, 
which after 24 hours’ standing assume a blue color (Dragendorf’). 
Zn I, = 318,019. 

Tests. Zinc iodide crystallizes from watery solution in deliques- 
cent regular octahedra. It melts at 446° C., and at higher tempera- 
ture sublimes without decomposition, forming needle-shaped 
crystals. For the purposes above stated the salt is sufficiently 
pure if when dissolved in starch solution it gives no eg ebs even 
when dilute sulphuric acid is added. 

PREPARATION. 64.905 parts of finely powdered zinc are rubbed 
in a mortar with 126.557 parts of iodine until the color has disap- 
peared, and then either sublimed or dissolved in water and the 
crystals well dried and preserved. 

The starch solution containing zinc todide, used for detection of 
nitrites in drinking water, etc.,is made by dissolviug 4 gr. of 
starch in a boiling solution of 20 gr. zine chloride in 100 Ce. of 
water, adding 2 gr. of zinc iodide, filling up toa litre and filtering. 
The solution should be placed into small vials and kept in the 
dark. 

ZINC SULPHATE, Zn S 0:1 + 7 H2 0. 


Ussrs. In the analysis of gaswater, zinc sulphate serves to pre- 
cipitate the sulphocarbonates; the precipitate, after washing with 
cold water, is brought into a flask containing water connected 
with a receiver containing tri-ethyl-phosphine. When heated to 
boiling the zine sulphocarbonate decomposes and the vapor of 
C S2is absorbed by the tri-ethyl-phosphine. ZnSOs4+ 7 He O = 
286.449. 

Tests. Zinc sulphate crystallizes in colorless, rhombic prisms, 
soluble at 15° in 0.67 parts, at 100° in 0.167 parts of water. Itis 
tested for impurities in the same manner as the metal, but for the . 
above use the commercial article, free frum iron, is sufficiently 
pure. 

PREPARATION. Pure zinc is dissolved in dilute sulphuric acid 
and crystallized. 


212 ZINC SULPHYDRATE—ADDENDA. 


ZINC SULPHHYDRATE, Zn (S H)2, 


Usss. To prepare pure hydrogen sulphide, free from arsenic, 
Hager proposes to use zine sulphhydrate, Zn (S H)., formed into 
pencils. Itis also used to detect free mineral acids in vinegar by 
the liberation of He 8; pure acetic acid does not decompose it 
(foehringer). Zn (S H)o = 180.878. 

PREPARATION. Purezinc sulphate is either precipitated by am- 
monium sulphide and the white precipitate washed and dried, or the 
sulphate is boiled with pure sulphur and potassium hydrate, and 
the washed precipitate moulded into pencils with 10% of white 
bolus (Hager). 


ADDENDA. 
BENZOYL CHLORIDE, Ce Hs, CO CI. 


Ussrs. For detection of alcohol, which is converted by it into 
ethyl benzoate, Ce Hs.C OO. Ce Hs, an ester of peculiar pleasant 
odor, even when only a small quantity is presentin water. The 
ester dissolves in the surplus of benzoyl chloride, whose disagree- 
able penetrating odor disguises that of the ethyl benzoate. Addi- 
tion of potassium hydrate solution decomposes the surplus of 
benzoyl chloride, while ethyl benzoate remains unaffected, and 
may now be recognized by its odor. A few Ce. of liquid contain- 
ing 0.1% of alcohol give a decided reaction (Berthelot). 

Benzoyl chloride has also been recommended by Baumann (and 
his collaborators, Goldmann, Wedenski and Udransky) to detect 
cystine in urine, ete., by converting it in alkaline solution into the 
insoluble sodium compound of benzoyl]-cystine, in which the cys- 
tine is recognized by its sulphur reaction, ete. Also for precipi- 
tating glucose from urine made alkaline by sodium hydrate, asa 
benzoyl compound in which the glucose may be identified by the red 
eolor reaction it gives with alpha-naphthol and conc. sulphuric 
acid. CsHs.COCl = 140.148. 

Txsts. Benzoyl chloride is a highly refractive liquid of pene- 
trating disagreeable odor, spec. gray. 1.25 at 15° C. By aidofa 
freezing mixture it is obtained in transparent crystals, which melt 
at —1° C. and boil at 198.389 C. It easily dissolves in ether and car- 
bon disulphide. Water decomposes it, slowly at ordinary tem- 
perature, rapidly when hot, into benzoic and hydrochloric acid, 
It is sufficiently pure when it forms ethyl benzoate with alcohol, 
recognized by its pleasant odor after the surplus of benzoyl chlo- 
ride has been decomposed by potassium hydrate. 


CADMIUM CHLORIDE—CARBAZOL, 213 


PREPARATION. Four parts of benzoic acid are distilled with 7 
parts of phosphorus pentachloride, the distillate is receivedina 
flask surrounded by a freezing mixture, and the crystals, after 
draining, are purified by redistillation, preserving the fraction 
distilling near 198°to C. 


CADMIUM CHLORIDE, Cd Cl, + 2 H: O. 


Usres. Cadmium chloride very rapidly and completely precipi- 
tates from even very dilute solutions of hydrogen sulphide or alka- 
line sulphides, all of the sulphur as yellow cadmium sulphide, but 
is not affected by hyposulphites (thiosulphates). Hence, itis used 
in the analysis of mineral waters to precipitate together all the 
sulphur present as alkaline sulphide or free hydrogen sulphide. 
The precipitate very frequently carries down with it some unde- 
composed cadmium chloride. 

Tests. Cadmium chloride forms colorless prisms of the form- 
ula Cd Cl, + 2H, O, which easily lose water in dry air or by 
heating. At 20° C. 100 parts of water dissolve 140.8 of Cd Cle. 
The anhydrous salt melts at 541° C.and at higher temperature 
Sublimes unchanged, forming colorless, shining scales. The solu- 
tion, slightly acidulated by H Cl, should yield with He S a precipi- 
tate of pure yellow color. The filtrate from this should, on evapo- 
ration, leave no permanent residue. The yellow precipitate should 
yield nothing to ammonia water (absence of arsenic). 

PREPARATION. Pure metallic cadmium is dissolved in some- 
what diluted hydrochloric acid. The solution is hastened by con- 
tact with metallic platinum (wire or foil). The concentrated solu- 
tion is crystallized and, if great purity is desired, is sublimed. 


CARBAZOL (Cs H:), N H. 


Usts. A solution of carbazol in conc. sulphuric acid, of spec. 
gr. 1.84, assumes a green color in contact with nitrates, nitrites, 
chromates, ferric salts, chlorine, bromine, iodine and other oxi- 
dizing agents. So intense is this green color, that even 0.0027 
mer. of nitric acid render it distinctly visible. Hence, it is recom- 
mended for detection of nitrates in drinking water, and their 
rapid colorimetric determination by comparison with the color 
produced in standard solutions of pctassium nitrate. The water, 
if necessary, is freed from iron by alkaline hydrate and from chlo- 
rides by silver sulphate, and 2 Cc. are mixed with 4 Ce. of cone. 
sulphuric acid and cooled. To this 1 Cc. of the solution of car- 
bazol is added, and after thorough mixing the color is compared 
with that of the standard (Hooker). 


214 CARBON DIOXIDE—CINCHONINE. 


TrEsts. Carbazol or diphenylimide crystallizes in shining white 
scales, which melt at 288° C. and sublime unchanged at 352° C. It 
is insoluble in water, slightly soluble in cold, more in hot alcohol, 
ether, chloroform, carbon disulphide, benzol and glacial acetic 
acid, and quite readily in conc. sulphuric acid. The latter solu- 
tion, at first brownish-yellow, turns olive green after some hours, 
while that in acetic acid remains unchanged for a considerable 
time. The crude article, obtained as a bye-product of the manu- 
facture of aniline and of anthracene, is sufficiently pure if its so. 
lution turns intensely green with a trace of nitric acid. 

PREPARATION. During the manufacture of anthracene the frac- 
tion distilling between 320° and 860° C. is preserved separately, 
and from it the carbazol contained in it is extracted by acetic 
ether. From the dry extract pure carbazol may be obtained by 
dissolving in toluol and adding picric acid. The carbazol picrate 
separates inred prismatic crystals. These are treated with am- 
monia water, when carbazol remains insoluble, while ammonium 
picrate dissolves. The product is purified by recrystallizing from 
hot absolute alcohol. 


CARBON DIOXIDE, C 02. 


_Usxs. To displace the air in apparatus during the distillation 
of easily oxidized substances, or when the presence of either oxy- 
gen or nitrogen would be objectionable, as in elementary organic 
analysis, for nitrogen determination, according to Dumas, where 
carbon dioxide is introduced, either into the open combustion tube 
from without or generated within the closed tube. Water satu- 
rated with carbon dioxide occasionally serves in the analysis of 
soils, to extract those carbonates insoluble in pure water, which 
by conversion into dicarbonates become soluble, the apparatus 
used permitting saturation under higher than ordinary atmos- 
pheric pressure. Also to extract bloodstains from cloth (Strwve). 

The gas used for these purposes is either liberated by heat from 
sodium dicarbonate, which yields C Ozand HzO, or, if the pres- 
ence of moisture is to be avoided, from anhydrous neutral sodium 
carbonate and potassium dichromate, or from manganous carbon- 
ate, ete. Or it is evolved from calcium or other carbonates by 
addition of hydrochloric aeid. In such case it must be purified by 
passing through wash bottle and drying apparatus. Pure mate- 
rials should be used to avoid introduction of volatile impurities. 


CINCHONINE, Cio He No O. 


Uses. Solution of the sulphate is used to distinguish tannic 
acid, whose solution is precipitated, from gallic acid, which is not 


ALPHA-NAPHTHYL-AMINA, 215 


precipitated by cinchonine (or other alkaloids). It also serves for 
volumetric determination of querco-tannic acid, according to 
Wagner’s method, by means of a solution containing 4.523 gr. of 
cinchonine sulphate in 1 litre, corresponding to 10 gr. of querco- 
tannic acid. The method is not very accurate. The nitrate is 
used with potassium iodide to detect bismuth, in nitric acid solu- 
tion, by an orange precipitate (Leger). 1 gr. cinchonine, dissolved 
in dilute nitric acid, is added to a solution of 2 gr. potassium 
iodide and water enough to make 100 Ce. The pharmacopeial 
preparation is of sufficient purity. Ci9 He Ne O = 293.408. 


_ Ethylic ether, page 102; when a specimen is shaken in a test tube 
with a drop of mercury the metal should remain perfectly bright. 
a tarnish indicates the presence of sulphur (ZL. L. de Koninck). 


Alpha-NAPHTHYL-AMINE, Cio Hz N He. 


Uses. For the detection of nitrous acid, which, with the solution 
of alpha-naphthyl-amine in glacial acetic acid, produces a yellow 
color, turning violet-red on addition of hydrochloric acid. Also for 
detection of hydrogen dioxide and other active oxidizers, which 
convert anaphthyl-amine, in aqueous solution, into violet-blue 
oxy-naphthylamine or naphthameine (Wurster). 

In conjunction with sulphanilic acid, it serves as Griess’ reagent 
to detect small quantities of nitrites, see page 20. Hydrogen di- 
oxide, which, especially in presence of sodium ehloride, converts 
ammonia into nitrites, may thus be detected by Griess’ reagent in 
minute quantities, as in saliva. If urea, leucine, tyrosine or simila1 
amido-derivatives are present, together with the nitrite, the sulph 
anilic acid of Griess’ reagent is decomposed by them and the 
violet-blue color of naphthameine appears, the same as if the 
anaphthyl-amine were used alone (Wurster). Cio H7 N H,=1382.761. 

Tests. Commercial alpha-naphthyl-amine, after recrystalliza- 
tion from alcohol, is sufficiently pure for the reactions above de- 
scribed. It is prepared in large quantities by the reduction of 
nitro-naphthalin for the manufacture of magdala-red and other 
diazo-colors. It forms white crystalline masses, sometimes with a 
gray or brownish tint. It has a penetrating, unpleasant odor 
which distinguishes it from the inodorous beta-naphthyl-amine. 
It melts at 50° and boils at 300°C. Itis quite soluble in alcohol, 
ether, glacial acetic acid or aniline, but requires 600 parts of cold 
water for solution. As the solution deteriorates by keeping, it 
should only be made in small quantities shortly before using, and, 
if preserved at all, should, be kept dark and closely guarded 


14* 


216 USE OF THE SPECTROSCOPE. 


against accidental absorption of nitrous fumes. The solutions for 
Griess’ test for nitrites are made as follows: 0.1 gramme of szwl- 
phanilic acid (see page 20) is dissolved in 80 Cc. of dilute acetic 
acid; 0.1 gr. anaphthyl-amine is boiled with 20 Ce. aistilled water, 
decanted from the blueish residue, and added to 180 Ce. of dilute 
acetic acid. The liquid to be examined is then mixed with half its vol- 
ume of the sulphanilic solution, heated to 80° C. and the naphthyl- 
amine gradually added until the color, at first yellow, turns red 
(llosvay). If very carefully preserved, the solutions may be 
mixed and added to the specimen. 


USE OF THE SPECTROSOCOPE. 


When white light passes through a prism whose planes meet at 
an acute angle, the rays composing it are dispersed into a color- 
spectrum, in which the violet rays are refracted farthest from their 
original direction, the red rays least. If a screen with a narrow 
slit is interposed between the source of light and the prism, the 
eolorbands of the spectrum are yet continuous if the light emit- 
ted contains all the rays composing white light. Butif the source 
of light emits only rays of one color, then the image of the slit 
appears as a bright line of that color. If rays of several colors 
are emitted from the source of light, we have a discontinuous or 
interrupted spectrum consisting of images of the slit in the several 
colors With dark spaces between, and giving the appearance of 
bright colored lines upon a dark background. Light emitted by 
solids at white heat produces a continuousspectrum. A platinum 
wire held in the flame until it becomes incandescent, or the bright 
flame of the gas-lamp or candle containing incandescent carbon, 
give white light and a continuous spectrum. Gases or vapors, 
when sufficiently heated to becomeluminous, emit, under ordinary 
pressure, color rays which are dispersed into an interrupted spec- 
trum of bright lines ; with increasing pressure and density these 
lines spread into diffuse luminous bands, and finally form a con- 
tinuous spectrum. A few solids, erbium, didymium and thulium, 
give, when heated, a continuous spectrum of moderate brightness 
as a background upon which certain brilliant lines are seen as an 
interrupted spectrum. When light of high intensity passes 
through transparent media, a portion of itisabsorbed. When 
this occurs uniformly for all rays, the spectrum merely loses some 
of its brilliancy. But when particular rays are absorbed more 
than others, certain parts will be wanting in the continuous spec- 
trum, and are represented by dark lines or bands. : 


USB OF THE SPECTROSCOPE. 217 

Of such origin are the dark lines in the solar spectrum, mapped 
by Fraunhofer in 1814, and since bearing his name. As ageneral 
rule, transparent media absorb those rays which they would emit 
when highly heated and colored substances absorb the rays of 
their complementary colors. Instruments for the observation of 
spectra, called spectroscopes, are of various construction, some 
very complicated and of powerful dispersion, for the use of as- 
tronomers, some very simple. 

In the following pages a concise description will be given of 
such phenomena only as may be observed by means of the simple 
spectral apparatus usually kept in analytical laboratories. The 
emission spectra of such metals and salts, as are capable of being 
produced at the temperature of the Bunsen gas burner, are valu- 
able means of their identification. Absorption spectra of solu- 
tions are also very useful for the recognition of coloring materials, 
etc. From the great number of the latter already described in 
works dealing especially with this topic, a few only have been 
selected, which are interesting, either on account of serving as 
color indicators, or forming the result of specific reactions, or 
being the means of identifying blood stains or poisoning by inha- 
lation of deleterious gases, or vice versa, recognizing the gas by 
the changes produced by it in the coloring matter of blood. 

Of the various instruments employed in the laboratory, the 
form adopted by Kirchoff and Bunsen is represented on plate 
VIJ, as constructed in the simplest manner by Desaga and 
others. A flint glass prism, contained in a dark box, receives light 
through the adjustable slit at the end of one of the tubes, the 
spectrum is observed through a small. telescope. For measuring 
the position of the colored images of the slit which form the 
lines of the spectrum, a photographed scale is inserted into the end 
of a third tube, and reflected so as to coincide with the color spee- 
trum observed by the telescope. A small prism, covering half the 
length of the slit, is often added, to introduce spectra of known 
substances, exactly superimposed over those of the substance 
under examination, so as to recognize coincidences and differences 
by comparison. . 

In more elaborate instruments the telescope turns upon a pivot, 
and the position of the lines is determined by measuring their 
angular difference upon a graduated are provided with nonius. 
Another form of instrument, the direct vision spectroscope, con- 
tains, in a straight tube, a number of small prisms (from 8 to 7), 
arranged to refract the rays of light so as to leave the instru- 
ment nearly in the same direction in which they entered. The 
plate represents the instrument devised by Prof. Vogel, which, in 


218 USE OF THE SPECTROSCOPE. 


addition to the slit and the prisms, has a collimator lens, and a 
mirror to reflect light from a second flame upon the comparison 
prism. No arrangement, for measuring the position of lines, is 
attached to this instrument; in observing flame spectra, the com- 
parison prism answers as a substitute, while for absorption spec- 
tra, observed with reflected solar light, the position of the Fraun- 
hofer lines, seen at the same time, serves as a guide. 

For accurately recording the position of lines and bands, it is 
best to give the wave length (X) of the ray, which is generally 
done in millionths of a millimetre. For ordinary purposes, dia- 
grams with a scale attached suffice, but it must be remembered 
that all spectra produced by refraction, not only differ according 
to the density of the glass or other material of the prism, but also 
condense the red end of the spectrum out of all proportion with 
the violetend. This will best be seen by comparison with the 
diffraction spectrum, produced by a fine grating, in which the 
lines, differing by an equal measure of their wave-lengths, ap- 
pear at equal distances from each other, while equal differences 
in wave-length are distorted to very unequal measures in the 
spectrum produced by refraction by prisms (see plate). In the 
plates illustrating this chapter, the refraction spectra are repre- 
sented as seen with the instruments in common use. The scale, 
immediately below the spectrum, indicates the wave-length (\), 
the figures from 40 to 80, representing one hundred thousandths of 
millimetres, as there is not room to give the third figure (400 to 800) 
necessary for the usual expression of waye-lengths in millionths 
of one millimetre. 

When an observation is to be made, the instrument is first di- 
rected towards the clear sky, or a white wall, and the opening of 
the slit and adjustment of the focus of the eyepiece so arranged 
as to give the sharpest possible definition of the fine dark lines 
running parallel to the colorbands. Of these lines, the most 
prominent ones were designated by Fraunhofer by letters of the 
alphabet, beginning at the red end of the spectrum. When the 
instrument is directed to the sun’s disk, a very brilliant spectrum | 
appears extending from near the line A, in the red, to beyond the 
line H in the violet end of the spectrum. Such a sight, however, 
must be taken with extreme caution, and for seconds only, as it 
might injure the eye. It is best to use the reflected light of a 
bright sky or a white wall, when a portion of each end of the 
colorspectrum will become shaded (see plate VIII, 1, sun. The 
position of the colorbands is indicated at the bottom of each 
plate). The instrument is then secured in this position, if absorp- 
tion spectra are to be observed, and a suitable holder arranged 


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USE OF THE SPECTROSCOPH, 219 


for placing the tubes, holding the colored liquids between the slit 
and the source of light. <A bright flame may be substituted for 
reflected sunlight, but has the disadvantage that it shows no 
Fraunhofer lines, and these valuable guides to the position of the 
absorption bands must be dispensed with. The tubes for holding 
the solutions may be either ordinary test tubes, of 1 Cm. diameter, 
or glass cells with flat parallel sides, or of wedge shape, so as to 
allow the examination of different thicknesses of the liquid. 


To observe the emission spectra of colored flames, the instru- 
ment, after focussing, is directed (with the slit perpendicular) 
toward the centre of the upper part of a narrow, non-luminous 
Bunsen flame, into the lower part of which the substance is in- 
troduced, supported on a platinum wire. Use of a broad flame, or 
directing toward the edge, or an oblique position of the slit, will 
give rise to secondary images, which greatly interfere with the 
accuracy of the result. The platinum wire is supported ona 
stand, and by adjustment in height and rotation can be easily 
brought and steadily maintained in any part of the flame most 
suitable for the volatilization of the substance. The wire, about 
0.5 to 0.6 Mm. thick, is bent into a loop of a width differing with 
the fusibility of the substance, and must be thoroughly cleansed 
before each observation by first soaking in water or dilute acid, 
rinsing in distilled water and then heating in the hottest part of 
the flame until it no longer produces either color or even the 
faintest spectrum. It is then charged with the substance to be ex- 
amined, either by immersing the redhot wire-loop into its powder, 
or by fusing a bead to it in the flame, or by means of the blow- 
pipe. In some cases it may be dipped into the solution. The 
spectrum must be observed accurately at the first insertion of the 
substance into the flame, as some substances are very volatile or 
are rapidly decomposed, and then fail to give the characteristic 
spectrum of their volatile salts (e.g. Ca Cl,). The observation 
must then continue for some time, to give opportunity for the 
more volatile substances, whose brilliant spectrum obscures the 
fainter lines, to evaporate. ‘The observer must make himself 
familiar with the spectrum of the Bunsen flame (see plate, VIII, 21 
C QO), so as not to confound its lines (which in instruments of small 
dispersion coalesce into broad but faint lines) with similarly situa- 
ted lines, especially those of boracic acid (see plate, LX, 14, Bz Os). 


EMISSION SPECTRA of the following metals and of some of 
their salts may be produced at the temperature of the Bunsen 
flame : 


220 ‘USE OF THE SPECTROSCOPE. 


Lithium, sodium, potassium, rubidium, eczsium, calcium, stron- 
tium, barium, magnesium (metal only), thallium, indium, gallium, 
lead, copper, cadmium, gold, tin and manganese. 

The lesser volatility of the more refractory metals forbids their 
recognition by flame spectra, and the electric spark or Geissler 
tubes must be resorted to, or fusible glasses, colored by their salts, 
may be prepared in films and their absorption spectra observed, 
e. g. cobalt, erbium, didymium. 

Too great a volatility also interferes by evaporating the sub- 
stance before it attains the temperature of luminosity, and thus 
most metalloids give no flame emission spectra. Those of carbon 
(C O, plate, VIII, 2), and boron (Be Os, plate, TX, 14), are most easily 
obtained, while those of sulphur, selenium, tellurium, phosphorus, 
arsenic, chlorine, iodine, etc., are obtained, only with great diffi- 
culty, by burning the vapor mixed with hydrogen, or byrendering 
it luminous in Geissler tubes. 

The lines composing the spectrum of an element are designated 
in order of their prominence and brillianey by the chemical sym- 
bol of the element followed by letters of the Greek alphabet. 
The following are the spectra of most importance to the analyst : 


Lituium (VIII, 8) at lower flame temperatures shows a single bril- 
liant red line, Li a, at670.6. At higher temperatures Lid appears 
at 610.2, nearer to the sodium line D and much fainter. The blue 
line at 460.4 is only produced by the high temperature of the elec- 
tric are. 


Soprum (VIII,4) shows, with low dispersion,a single yellow line at 
589.5, corresponing to D in the solar spectrum. This is subdivided 
into two lines by higher dispersion, and these again are resolved 
into groups by the best instruments. ‘The line is so intensely 
bright that even the smallest traces of sodium (dust floating in the 
air, etc.) produce it, and it is difficult to obtain a spectrum in 
which the line does not flash up occasionally. This, however, is 
sometimes of use for estimating the position of other lines. 


Potassium (VIII,5) ordinarily shows but a single line in the red,K 
a, at 769.8, near A. With better instruments, a faint line is visible 
at 766.2. At higher temperature (burning of K N Os or K Cl Os) 
K dis seen as a sharp line in the violet end at 404.4, which at low- 
er. temperature appears as afaint halo only. The luminosity in 
the centre of the spectrum is by higher power resolved into many 
lines. 


RuBipiIuM (VIII,6) shows, with feeble dispersion, 2 lines, one red, 
the other deep blue ; with more powerful instruments both of these, 











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USE OF THE SPECTROSCOPE. 221 


are resolved into double lines, while the faint luminosity in the 
orange, yellow and green is resolved, at high temperature, into 
lines as shown in the plate. The blue lines are: Rba at 421.6 and 
Rb 0 at 420.2 ; the red lines: Rbc at 780.0 and Rb d at 795.1. 


CaxEsium (VIII, 7) gives a spectrum similar to rubidium, but the 
brillant lines are brighter blue and the fainter line orange instead 
-of red. Cs @ at 156.0; Cs bat 459.7; Cs c at 621.9. The other 
lines at lower temperature coalesce into a luminous halo, but ap- 
pear, at higher temperature, as distinct lines. The volatility of 
caesium causes a rapid disappearance of its spectrum. 


CALcium (1X,8) shows two very prominent lines: an orange one, 
Ca @ 620.6; a green one, Ca 6 at 555.38; a somewhat fainter violet 
blue, Cac at 428.6, nearly coincident with the rubidium line, and 
a number of finer ones in red, orange and yellow. The orange 
and green lines persevere longest, though fainter after the decom- 
position of the volatile chloride, and become more brilliant again 
on moistening the platinum wire with hydrochloric acid. 


STRONTIUM (IX,9) shows seven lines in the redand orange and one 
fine blue. The wavelengths of the brightest are Sr @ 603.1; Srd 
667.0; Sr c 658.5 ; Sr d 460.8. 


Barium (IX,10) has a number of fine linesin the orange, yellow and 
green portion of the spectrum, of which the brightest are, three 
in the green, Ba a at 524.0; Ba ) at 518.0; and Bad at 585.0, nearly 
coincident with the single green line of thallium. Greenish-yel- 
low, Ba ¢ at 553.5; orange, Ba e at 606.2; besides several fainter 
lines and bands in red, orange, yellow and green. 


MaGnesium (IX, 11) shows a flame spectrum only when the 
metal is burnt, when a triple green line, corresponding to Fraun- 
hofer b appears at 516.7, 517.2 and 518.8, anda faint blue band near 
the F line. When magnesium salts are added to an alcoholic so- 
lution of purpurin (a coloring material derived from madder), to 
which a solution of ammonia and ammonium chloride had been 
previously added, peculiar absorption bands appear on each side of 
the Eline in addition to the normal absorption of purpurin (see 
plate No. 29). They are very similar to those produced in the same 
solution by aluminium salts, but disappear upon addition of acid 
while those of aluminium remain. 


THALLIUM (IX, 12) shows a very brilliant single green line at 
584.9, nearly coincident with Ba c, and at higher temperature a 
faint yellow line at 568.0. : 


222 USE OF THE SPECTROSCOPE. 


Inpium (IX, 18) in the flame shows a bright indigo line at 451.0. 
Three other bright lines are produced by the electric spark : a 
violet at 410.1, a green line at 525.0, and an orange at 619.3. 


GALLIUM in the flame shows a feeble violet line at 417.0 ; anoth- 
er at 403.1 becomes visible by the spark. 


LEAD OXxIpE, at the temperature of the Bunsen flame, shows a 
number of lines, of which one orange, at 626.0; one yellow, at 
570.0; one greenish, at 548.0, and two green lines at 534.5 and 518.7, 
are brightest. 


CoPpPpER CHLORIDE colors the flame differently, according to the 
quantity introduced. With a larger quantity the nucleus is or- 
ange, with a blue and a green outer envelope; as decomposition 
proceeds, the nucleus becomes first blue, then green. The spec- 
trum shows many lines at 650.0, 626.0, 608.0, 550.0, 541.0, 584.0, 497.5, 
486.5, 481.0, 476.5, 454.0, 450.5, 445.5, 442.8 and 488.0. Of these, 
three greenish-yellow lines are brightest, while the nucleus is 
orange. They fade as the nucleus becomes blue, while the other 
lines gradually appear. When the nucleus of the flame turns 
green the lines become fainter, while diffuse bands appear. 


CADMIUM shows a green line at 508.5 and two blue at 479.9 and 
467.7. 


GOLD CHLORIDE colors the flame green and gives a spectrum of 
7 lines at 479.3, 506.8, 523.0, 565.8, 572.7, 583.6 and 627.8. 


Tin. Stannous chloride and other volatile tin salts color the tip 
of the flame red, and the spectrum shows diffuse bands near 645, 
580, 560 and 450. 


MANGANOUS CHLORIDE shows a flame spectrum of 6 groups near 
620, 580, 550, 580, 520 and 500, which, by instruments of higher dis- 
persion, are resolved into many lines. Other compounds of man- 
ganese give, at higher temperature (Bessemer converter), many 
more bright lines in the blue and violet. 


CarBoN Monoxtpe (VIII, 2) shows diffuse bands in orange, 
yellow, green, blue and indigo, which coalesce into lines in in- 
struments of low dispersion, but by higher powers are resolved 
into distinct lines. The brightest lines are in orange from 618.7 
to 595.4; in yellow, from 563.3 to 546.6; in green, from 516.4 to 
509.8 ; in blue, from 473.6 to 468.2 ; in indigo, from 488.1 to 481.1. 
They are best observed in the lower cooler part of the Bunsen 
flame, but appear in the flame of all carbon compounds. 


USE OF THE SPECTROSCOPE. 223 


Boron TRIOXIDE (IX, 14) and boracic acid, Hs B Os, color the 
outer envelope of the flame green and produce a spectrum com- 
posed of diffuse bands at 580.7, 548.5, 548.9, 519.2, 494.1 and 472.1 ; 
also lines at 639.7, 621.0, 604.1 and 452.9. 

The emission spectra of erbiwm, didymium and thulium are seen, 
when the oxides or salts are heated to incandescence, as bright 
lines upon a background of a continuous spectrum. 


ABSORPTION SPECTRA of some metals may be observed by 
fusing them with borax, microcosmic salt or alkaline silicates and 
forming a thin film of the fused mass between the sides of the pla- 
tinum wire loop. With some it suffices to interpose a solution 
between the source of light and the instrument. Some give the 
absorption lines or bands when the light reflected by them is exam- 
ined in the spectroscope. 


ERBIUM CHLORIDE (XII, 33) shows 3 absorption lines, having 
wavelengths of 653.4, 523.1 and 487.4. Its emission spectrum is 
similar. . 

DIpYMIuM CHLORIDE (XII, 34) shows 8 lines at 780.7, 578.8, 574.7, 
571.9, 521.9, 520.5, 482.2 and 469.1, either bright, when heated, or 
as absorption lines. 


THULIUM OXIDE, when heated, shows upon a continuous spec- 
trum as background a bright red line at 684.0 and a blue one at 
476.0. Its salts show two absorption bands at 684.0 and at 465.0. 


POTASSIUM PERMANGANATE (XII, 32) in aqueous solution shows 
a remarkable absorption reaching from 589.0 to 482.0, in which 5 dis- 
tinct bands are shown at certain dilutions (0.01%), of which the 
second one, counting from the red end, is the strongest. With 
greater concentration of the solution the 83 middle ones coalesce ; 
in greater dilution all gradually fade, and at last only the second 
band remains visible. 


CoBALT SULPHOCYANATE (XII, 35) yields with ether a violet-blue 
solution whose absorption spectrum, visible even in great dilution, 
is very characteristic. The violet end is shaded to G, then a nar- 
row absorption band occurs at 560, and a very broad and dark one 
from 602.0 to 660.0; from thence a dimly lighted interval reaches 
to 700.0, and the rest of the red end is dark. 


When organic liquids showing absorption spectra of one or more 
bands are to be examined, it is almost indispensable to use the ac- 
cessory prism for bringing the spectrum of a substance of known 
purity into contact with the one to be investigated. The appear- 
ance of the two superimposed spectra then resembles those on the 


224 . USE OF THE SPECTROSOOPE, — 







plates Nos. 18, 20 and 21, and admits of close comparison a 
- accurate observation of coincidences or differences. | With he 
coloring material a change of the solvent often prodnee 
marked and decided differences, and the degree of satural 
dilution gives rise to various appearances. 

For the observation of these absorptions, an instrument of 
moderate dispersion is preferable to one of high power, and the 
ordinary pocket spectroscope is quite sufficient for such work if 
provided with a prism for comparison. Great help is also derived 
from a wavelength scale engraved on a glass disk and inserted in- 
to the focus of the ocular. When minimal amounts of blood or 
other coloring matters are to be examined, the spectroscope is 
sometimes used in combination with the microscope by inserting 
it into the place of the ocular. 

Considerable difficulty is sometimes experienced when substan- 
ces produce mixed spectra. Thus blood partially saturated with 
carbon monoxide gives the mixed spectra of oxyhaemoglobin (XI, 
23) and C O haemoglobin (XI, 25), and is difficult to distinguish 
from the spectrum of pure reduced haemoglobin (XI, 24). In 
such cases the superimposing of spectra of known substances for 
comparison and the addition of reagents to the liquid will often 
decide the question, for a number of spectra are changed in posi- 
tion by the addition of a drop of acid or alkali, by shaking with 
air, etc. 


BRAZILIN (X, 15), see page 58, in aqueous solution shows a dark 
band from E toward D, the nucleus extending from 527 to 557, with 
gradual shading off at both ends. The red end of the spectrum is 
absorbed from a, the violet end from half way between b and F 
increasing gradually towards the more refrangible end. It may 
be readily mistaken for oxyhaemoglobin in sufficient concentra- 
tion to let its central bands coalesce (XI, 22). Addition of a little 
acid clears up the absorption band of brazilin, while alkalies in- 
crease its intensity. 


CoCHINEAL (X, 16, 17), see page 77, contains the glucoside car- 
minic act {, which by the action of alum may be split up into car- 
mine red and glucose. Both give similar spectra. Carminic acid 
absorbs the violet end completely to 450.0, G, and then shades off 
gradually to 460.0 between Eand D; two dark bands occur with 
slight shading between. Addition of alkali completely clears up 
the intervening space and moves the bands somewhat towards the 
redend. Carmine red absorbs the violet, beginning at 412.0 and 
gradually darkening toward the end. The two central bands are 
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USE OF THE SPECTROSCOPE. 225 


darker than that of the carminic acid, and extends from 500 to 530, 
the other from 550 to 570. Addition of alkali moves both toward 
the red end (see plate X, 17). There is great danger of mistaking 
carminic acid for haemoglobin (compare XI, 23 with X, 16). 


Eostn (X, 18), see page 79. The red, aqueous solution of the 
commercial potassium salt fluoresces strongly. Addition of acids 
destroys this fluorescence, alkalies restore it. The acid solution 
has two slightly shaded bands, one uniting the lines E and b, the 
other on both sides of F. Addition of alkali increases the dark- 
ness of the first, and the two not only coalesce, but spread from 
470 to 580. The ends of the spectrum show no other absorption 
beyond that occasioned by the reflection of the solar light in 
which they are observed. The spectrum is easily distinguished 
from those of blood. 


NAPHTHALIN RED (X, 20), also called Magdala red, in alcoholic 
solution forms a spectrum which might be easily mistaken for that 
of oxyhaemoglobin. The darkest band reaches from 575 to 545 a, 
the lighter shaded one from 520 to 500; no other absorption at the 
ends of thespectrum. The watery solution shows only the dimmer 
of the two bands from 530 to 500. 


SAFRANINE (X, 21), see page 176, in acid solution has two faint 
absorption bands, coincident with but much broader than those of 
C O haematin (XI, 28); they reach from 610 to 570 and from 540 to 
500. On addition of alkali the first one of the bands disappears, 
the second darkens and extends considerably towards the more 
refrangible end, from 550 to 475. No absorption at the ends be- 
yond that by reflection of the sunlight. 


FURFUROL-UREA (X, 19). The purple solutionresulting from the 
mixture of furfurol, urea and hydrochloric acid, shows two broad 
and dark absorption bands, one from 600 to 565, another from 500 
to 471, both with lighter shades added to each side; the red end of 
the spectrum is shaded up to 670. (See on page 105.) 


BLoop may be recognized readily by the absorption spectra of 
its coloring matters and their modifications by absorption of gases. 

Haemoglobin (cruorin) readily absorbs the atmospheric oxygen 
and becomes oxyhaemoglobin, or may be oxidized by permanganate, 
etc., to methaemoglobin. Heating, especially with acids or alkalies, 
converts haemoglobin into haematin, whose hydrochlorate is 
known as haemin. All of these give characteristic spectra. 


OXYHAEMOGLOBIN in concentrated solution (or fresh, normal 
blood) is impervious to light in tubes of 1 Om. diameter. As 


226 USE OF THE SPECTROSCOPE, 


the solution is diluted to 1% it shows a narrow strip of red, 
which with greater dilution expands, and when the solution con- 
tains 0.8% shows the spectrum No. 22, having a dark band from D 
to half way between E and b, with a lighter shade added to each 
end, so as to reach from 597 to 5138, while the violet end of the 
spectrum is entirely obscured from 500 to the end. Greater dilu- 
tion (see No. 23) makes this shade lighten and recede to 460, while 
the broad central band separates into a narrow dark band from 
590 to 567, and a fainter one from 550 to 520. With still greater 
dilution these bands become narrower, and finally, in a 0.01% so- 
lution, only the darker one remains from 582 to 575. When the 
solution of oxyhaemoglobin is gently heated with a little weak 
solution of alkaline hydrate, the bands coalesce and move toward 
the red end, forming the spectrum of 


OXYHAEMATIN (XI, 26), characterized in dilute solution by a 
single band extending from 625 to 505. Greater concentration en- 
larges this band at both ends until the interval between it and 
the absorption from the violet end becomes shaded. 

When oxyhaematin is boiled with more concentrated alkaline 
hydrate, it is converted into reduced 


HAEMATIN (XI, 27), whose spectrum has 2 bands, a very dark 
one from 558 to-548, and a fainter one from 535 to 511; the shading 
of the violet end reaches only to 489. The addition of a little 
alcohol and oxalic acid in slight excess changes this spectrum to 
4 bands, one between C and D, one a little beyond D, a third 
broader one near E, and the broadest, fourth, near the F line. 


SULPHOHAEMOGLOBIN. When pure, this has a narrow absorp- 
tion band at 620, which is super-added to the spectrum of haemo- 
globin, when this has not been entirely converted. Itis produced 
by saturating blood with hydrogen sulphide or by reducing oxy- 
haemoglobin by yellow ammonium sulphide, when the oxyhae- 
moglobin bands disappear, while those of C O haemoglobin 
remain unaffected. . 


HAEMOGLOBIN, HAEMATOCRYSTALLIN or CRUORIN (XI, 24), as 
contained in blood after removal of the oxygen, shows violet and 
green dichroism. In dilution of 2% it shows a dark band from 
595 to 585, with a lighter interval near 575. It also absorbs the. 
violet from 408 to the end. After saturation with carbon monox- 
ide, blood contains no more oxyhaemoglobin, but, instead of it, 


C QO HAEMOGLOBIN; whose spectrum, to the careless observer, 
shows little difference from that of oxyhaemoglobin, but in reality 
has its. bands further removed from the red end and slightly less 








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dark. A light interval can be distinctly seen between the D line 
and the margin of the first band, which extends from 578 to 560. 
The second band reaches from 548 to 520. The difficulty of rec- 
ognizing the joint spectrum of C O haemoglobin and oxyhaemo- 
globin in blood only partly saturated with C O may be overcome 
by reduction of the oxyhaemoglobin by means of yellow ammo- 
nium sulphide (or, according to Jaederholm, by a mixture of 
rochelle salt and ammonium-ferrous sulphate), which eliminates 
the bands of oxhaemoglobin, but not those of C O haemoglobin. 
Another method of recognizing C O in blood, also proposed by 
Jaederholm, consists in the conversion into CO haematin. The 
blood is shaken in a test-tube with twice its volume of 30% sodium 
hydrate solution. The coagulum, in absence of C O, has a green- 
ish color, gradually turning into red-brown. If C O is present 
the color is red from the formation of C O haematin. From these 
coagula a watery solution is made for examination of the spec- 
trum. 


C O HAEMATIN (XI, 28) when unmixed shows two bands in near- 
ly the same position as oxyhaemoglobin, but fainter, extending 
from 589 (D) to 564 and from 545 to 526(E). When haematin is 
mixed with it the two bands combine by an intervalof lesser shade 
with a darker stripe near 550. 


Rep WINE (XII, 30) gives a spectrum greatly resembling that of 
fresh blood in 1% aqueous solution. The unshaded space of the 
spectrum extends only from 710 to 620; from thence a half-shade 
gradually increases in density towards the violet. Ondiluting 
the bright space extends more towards D. When made alkaline 
by addition of ammonia the shade recedes to E, but a dark band 
forms from 656. (C) to 610. In case of fraudulent coloration by 
malva, the same band extends 656 (C) to 540; when elderberries or 
whortleberries are used for coloring the band begins at 685 and ex. 
tends to 540, where it joins the half-shade, which gradually dark- 
ens towards the violet end. 


FucuHsIn (XII, 31) has a very dark band reaching from 587 (near 
D) to 517 (near b); no absorptionat the ends other than that by 
reflection of sunlight. It somewhat resembles the spectrum of 
haemoglobin. 


ANILINE BLUE shows a very dark absorption band from 656.2 (C) 
to 550, gradually shading off from there to 520 (between E and b). 
Diphenylamine blue and some other blues show a nearly identical 
spectrum. In mawve violet in concentrated solution, tne dark 
band begins at 670 and extends to 610, from whence it gradually 
shades off to 565. 


* 


228 USE OF THE SPECTROSCOPE, 

CHLOROPHYLL in alcoholic solution shows a number of dark 
stripes. Four of these coalesce by intervening half-shades into a 
band extending from 686.7 (B) to 536. The first, broadest and dark- 
est, from 686.7 to 645, remains visible even in great dilution. The 
other three are only produced by concentrated solutions. The 
second lays between 628 and 612, the third between 585 and 575, 
near the D line ; the fourth between 544 and 536. From the F line 
on a perfect absorption reaches to the violet end. In very dilute 
solution this resolyes into 8 darker bands with intervening half- 
shades. 


FRAUNHOFER LINES, produced by absorption in the solar atmos- 
phere by various elements, are designated by letters of the alpha- 
bet, and have the following wavelengths, expressed in millionths 
of a millimetre : 


A 760.400 Nitrogen. 
718.360 Nitrogen. 
686.710 Nitrogen. 
656.210 Hydrogen a. 

ys 589.513 Sodium a. 


Qwe 


D2 + 588.912 Sodium 6. 

3 \ 587.500 Helium. 
E 526.918 Iron. 
1 , 518.310 Nitrogen. 
2 ) 518.30 Magnesium. 
3 ) 517.20 Magnesium. 
4 \ 516.70 Magnesium. 
F 486.074 Hydrogen b. © 
G 480.725 Iron. 
h 410.120 Hydrogen d. 
H1 396.810 Hydrogen e (Ca, Fe). 
H2 893.300 Iron (Ca). 


b 


LIST OF TESTS, 229 


ios ek OF TESTS. 


Arranged under the names of the substances to which they are 
applied. 


Absinthin, sulphuric acid, brown changing to blueish-green. 

Absolute alcohol 27; anthraquinone 48; anhydrous cupric 
sulphate 96. 

Absolute ether 102; anthraquinone 43; aniline violet 102, 
potassium dichromate 102, 157. 

Acetal, Lieben’s iodoform test, iodine 110. 

Acetanilide 42; Hoffmann’s isonitril test, chloroform 71; po- 
tassium hydrate 162; potassium nitrite, Plugge’s reagent, 134, 167. 

Acetie acid and acetates 5; arsenic, Kakodyl test, 45; al- 
cohol, acetic ether test, 27; ferric chloride, 118; iodine, Lieben’s 
test, 110. 

Acetic ether 101. 

Acetone, picric acid 18, 205; Lieben’s test, iodine 110; sodium 
nitroprusside 191; sodium acid sulphite 196. 

Acetylene, cuprous chloride 93. 

Acids, free, gallic acid and ferrous sulphate 6; test papers and 
color reagents 19, 47, 76ff. Volumetric: ammonia 31; Kieffer’s so- 
lution, cuprammonium 100; potassium hydrate 162; sodium hy- 
drate 187, antipyrine and ritrites 44; dipterocarpus 101; ferric ace- 
tate, etc., 118; sugar 199; zinc sulphhydrate 212. 

Acids, inorganic, first group, barium chloride 49: second 
group, silver nitrate 178. 

Acids, organic, calcium chloride 63; ferric chloride 118. 

Aconitine, see alkaloids, phosphoric acid 17. 

Aesculin, sodium hypochlorite 187. 

Albumin 25; heat; nitric acid 14; metaphosphorie acid 17, 25; 
phosphotungstic acid 18; picric acid 18, 205; tannic acid 28; tri- 
chloracetic acid 25; ammonium sulphate, 38; basic cupric acetate 
92; gold chloride 107; basic lead acetate 120; lead chloride 121; 
lead hydrate 123; magnesium sulphate 126; mercuric chloride 129; 
Geissler’s solution 133; mercuric nitrite 133; nitrous ether 139; 
phenol 144; potassium ferrocyanide 160; potassium nitroprusside 
168; sodium nitroprusside 191. 


Alcohol, amyl, 26; methyl violet 85; potassium dichromate 
157. 


230 LIST OF TESTS. 


Alcohol, ethyl, 26; acetic ether with acetic acid 5; blue with 
Froehde’s reagent 12; carbon disulphide 66; in essential oils, fuch- 
sin 80; ether with sulphuric acid 102; potassium acetate 151; po 
tassium dichromate 157; sodium acetate 182; sodium | salicylate 
194; benzoyl chloride 212. 


Alcohol, methyl, 27; oxalic acid 28; potassium permanganate 
168; sodium salicylate 194. 


Alcohol, propenyl, glycerin, 28, 107; phenol 144; borax 
186; stannic chloride and pyrogallol 19, 208. 

Aldehyde, diazobenzol sulphonic acid 20; fuchsin-sulphur- 
ous acid 81; hydroxylamine 110; iodine, Lieben’s test, 110; phenyl- 
hydrazine 145; potassium hydrate 162; silver nitrate 178; sodium 
amalgam 182; sodium hydrate 187. 

Alkalies, caustic, 380, 162, 187; test papers and color rea- 
gents 19, 47, 76ff. Volumetric: hydrochloric acid 9; nitric acid 15; 
oxalic acid 16; sulphuric acid 28; tannic acid and iodine, Gries- 
mayer’s test, 28, 106; ammonia liberated from ammonium salts; 
potassium tetroxalate 168. 

Alkaline carbonates 81, 158, 183; in dicarbonates: magne- 
sium sulphate 126; mercuric chloride 130; see also acid potassium 
carbonate 155; in hydrates: calcium sulphate, see potassium hy- 
drate 162. 


Alkaline earths 48, 62, 128, 198. Volumetric: hydrochloric 
acid 9; nitric acid 15; ammonium carbonate 31; ammonium oxa- 
late 36; ammonium phosphate 37; soap solution 180; sodium phos- 
phate 192. 


Alkaline sulphides 88, 178, 195; cobalt paper 75; chloral 
hydrate 69; lead acetate 119; potassium nitroprusside 168; sodium 
nitroprusside 191. 


Alkaloids and glucosides; chromic acid 6; iodic acid 11; 
metatungstic acid 12; molybdie acid derivatives, De Vrij’s reagent 
12; Froehde’s reagent 12, 190; nitric acid 14; perchloric acid 16; 
phosphoric acid 16; phospho-antimoniec acid, Schultze’s reagent, 
17; phospho-tungstic acid, Scheibler’s reagent, 18; picrie acid 18, 205; 
silico-tungstic acid, Godeffroy’s reagent, 23; tannic acid 24; titanic 
acid 24; ammonium metavanadate 35; bismuth potassium iodide, 
Dragendorft’s reagent, 56; bromine 59; cadmium potassium iodide, 
Marme’s reagent, 62; cerium sulphate, Sonnenschein’s reagent, 67; 
chinoidine iodosulphate 68; chlorine 70; chloroform, ether, Prol- 
lius’ mixture 71, 108; gold chloride 107; iodine 110; iridium 
sodium chloride 112; ferric chloride 113; ferric ferricyanide 115; 


LIST OF TESTS. 231 


lead chloride 121; mercuric chloride 130; mercuric potassium 
iodide, Mayer’s reagent, 132; phenol 144; platinum chloride 149; 
potassium dichromate, Luchini’s reagent, 157; potassium platinum 
cyanide 160; potassium silver cyanide 160; potassium cupric 
cyanide 160; potassium ferrocyanide 160; potassium ferricyanide 
161; potassium hydrate 162; potassium iodate 164; potassium 
iodide 165; potassium permanganate, Wenzel’s reagent, 169; so- 
dium iodate 190; sodium molybdate 190; sodium nitroprusside 191; 
sodium salicylate 194; sodium selenate 194; sodium sulphantimon- 
ate 194; sodium tungstate 198; stannous chloride 208; zinc chloride 
210; zine iodide 211. 

Aloin, sulphuric and nitric acid: nataloin green, red then blue; 
barbaloin red. 

Alpha-naphthol 136; chloral hydrate 69; chloroform 71; 
glucose and sulphuric acid, Molisch’s test, 136. 

Alum, logwood 84; in bread, gelatin 106. 

Aluminium and salts 29; ammonium chloride 32; am- 
monium oxalate 36,37; ammonium succinate 38; cobaltous nitrate 
78; nitroso beta-naphthol 186; potassium sulphate 172; sodium 
acetate 182; sodium acid sulphate 195; trimethylamine 204; pur- 
purin, spectrum. 

Amido benzol, see aniline. 

Amido-dimethyl-aniline 48; ferric chloride and hydro- 
gen sulphide, methylene blue, 48. 

Amines, primary, citraconic acid 73. 

Ammonia and ammonium salts 30ff.; test papers and 
color reagents 19, 47, 76 ff.; fuchsine paper 81; logwood paper 85; 
hydrochloric acid 8; volumetric acid solutions 9, 15, 16, 23; rosolic 
acid 19; calcium hydrate 64; chloral hydrate and hydrogen sul- 
phide 69; sodio-cobaltic nitrite 75; cupric sulphate 96; Bohlig’s test 
131; Nessler’s test 182: mercurous nitrate 134; palladium paper 
141; phenol and hypochlorite 144; platinic chloride 149; potassium 
hydrate 162; potassium stannous chloride 171; sodium hydrate 187; 
sodium acid tartrate 196. 

Aniline 40; volumetric acid solutions 9, 15, 16, 28; blue with 
hydrochloric acid and pine wood 8; blue with fuming nitric acid 
14; green with sulphuric acid and lead dioxide; calcium hypochlor- 
ite 65; chloroform 71; ferric chloride 118; potassium dichromate 
157; potassium ferricyanide 161; potassium hypochlorite 164; sodium 
hypochlorite 187. 

Aniline dyes, chloroform 71; tannin reactive 182. 

Aniline parasulphonie acid, sulphanilic acid 20, 
naphthylamine and nitrites, red, 20; sodium amalgam and alde- 
hyde, red, 181. 


232 LIST OF TESTS. 


Anthraquinone 48; sodium amalgam and water, red, 44; 
sodium hydrosulphite, red, 189. 

Antifebrine, see Acetanilide. 

Antimony and salts, hydrogen sulphide, orange, 10; am- 
monium carbonate 31; Marsh’s test 45; hypochlorites 45, 65, 164, 
187; zinc, black spot, adhering to platinum foil 148, 208. 

Antipyrine 44; nitrous acid, green, 44, 167, 191; ferric chlor- 
ide, red, 44, 113. 

Apomorphine, see Alkaloids; nitric acid, red, 14; gold 
chloride, purple, 107; iodine, blood red, 110; ferric chloride, ame- 
thyst color, 118. 

Arsenic and its compounds 4d; acetic acid. kakody]l test, 
5, 151, 182; hydrogen sulphide, yellow, 10; ammonium carbonate 
31; ammonium sulphide 88. Arsenetted hydrogen tests: Marsh’s 
zine and acid, ignition, 8, 45, 91, 708; Fleitmann’s, zine and caustic 
alkali, silver nitrate, 14, 178, 208; Gatehouse’s, aluminium and caustic 
alkali, 29; Gutzeit’s, zinc and acid, silver nitrate 8, 117, 124, 147, 
178, 209; Hager’s, magnesium 123; calcium hypochlorite 45, 65; 
charcoal, reduction; copper, Reinsch’s test 91; cupric sulphate 96; 
cupri-tetrammonium sulphate, Scheele’s test, 99; mercuric chloride 
129; potassium hypochlorite 164; silver nitrate, Hume’s test, 178; 
sodium hypochlorite 187; sodium sulphite 195; stannous chloride, 
Bettendorff’s test, 203; uranium acetate 205. 

Aspidospermine, see Alkaloids, perchloric acid, red, 
16. 

Atropine, see Alkaloids, sulphuric acid, odor; phospho- 
antimonie acid 18; fuming nitric acid and alcoholic potassa, red; 
mercuric chloride, Gerrard’s test, red; potassium dichromate and 
sulphuric acid, odor, 157. 

Auric salts, see Gold, 107. 

Balsam gurjun, see Dipterocarpus oil, 101. 

Barium dioxide 50; titanic acid 24; potassium chromate 156. 

Barium salts 48; hydrofluosilicic acid 10; sulphurie acid and 
sulphates 21, 38, 66, 172, 195, 199; ammonium carbonate 31; potas- 
sium chromate, 156; potassium dichromate 157; sodium phosphate 
192; sodium tungstate 197; spectrum 221. 

Bases, metallic, barium group, ammonium carbonate 31, 
sodium phosphate 192; aluminium group and iron group: ammo- 
nium sulphide 88 (ammonia 380); copper and arsenic groups: hy- 
drogen sulphide 10. 

Bebeerine, see Alkaloids, bismuth potassium iodide 56, 
sodium chloride 185. 

Beer, mercuric potassium iodide 132; halimetric method, so- 
dium chloride 185; uranium acetate 205. 


é 


LIST OF TESTS. 233 

Benzidine, potassium dichromate 157. 

Benzin 58; dissolves iodine with red color. 

Benzoic acid and benzoates, ferric chloride 113. 

Benzol 54; dissolves iodine with violet color. 

Berberine, see Alkaloids, chlorine, blood red, 70; iodine 
and potassium iodide, green. 

- Beryllium, potassium hydrate 152. 

Bettendorff’s arsenic test, tin 202; stannous chloride 
2038. 

Bile acids, Pettenkoffer’s test, cane sugar and sulphuric 
acid 199. 

Bile Colors, nitric acid 14; bromine 59; methyl violet 85; 
iodine 110; potassium nitrite and sulphuric acid, green. 

Bilirubin, diazobenzol-sulphonic acid 20. 

Bismuth and salts 55; iodine 110; potassium chromate 156; 
potassium iodide 165; potassium stannous chloride, brown, 171; 
sulphur iodide 200. 

Blood; guaiacum 81; oil turpentine; potassium iodide 165; 
spectrum 225. 

Boettger’s test for glucose, bismuth subnitrate 57. 

Bohlig’s test for ammonia, mercuric oxychloride 131. 

Boneblack, caramel 66. 

Boracic acid and borates 5; hydrofluoric acid 9; methyl 
alcohol 27; glycerin 28, 186; turmeric 89; manganous sulphate, 
volumetric, 128. 

Brazilin 58; spectrum 224. 

Bromates, aniline sulphate 42; paratoluidine, blue, 143. 

Bromine and bromides 59; arsenic trioxide, volumetric, 
45; cadmium iodide 61; chlorine 70; cupric oxide, blowpipe test, 
95; cupric sulphate 96; lead dioxide 123; mercurous nitrate 134; 
palladious nitrate 142; phenol 144; potassium dichromate 157; po- 
tassium acid sulphate 173; silver nitrate 178; starch 197. 

Bromoform 60. 

Brucine 50; nitrie acid 14; perchloric acid 16; phospho-anti- 
monic acid 18; mercurous nitrate 134; sodium selenate 194; stan- 
nous chloride 208. 

Butter, phenol 144. 

Butyl alcohol, Lieben’s test 110. 

Cadmium and salts 91, hydrogen sulphide 10; ammonium 
benzoate 31; ammonium hyposulphite 35; potassium cyanide 159; 
sodium phosphate 192; sodium pyrophosphate, electrolytic, 193; 
spectrum 222. 

Caesium salts; sodio-cobaltic nitrite 75; platinic chloride 
149; stannous chloride 203; spectrum 221. 


234 LIST OF TESTS. 


Caffeine, see Alkaloids, phospho-antimoniec acid 18. 

Calcium salts 62; oxalic acid 15; ammonium carbonate 31; 
ammonium oxalate 36; soap solution 180; sodium tungstate 197; 
spectrum 221. 

Campari’s reagent for potassium, bismuth sodium 
hyposulphite 57. 

Cane sugar 199; sulphuric acid 21; inversion then glucose 
tests; phenyl hydrazine 145. 

Caprylic alcohol; Lieben’s test 110. 

Caramel 66; boneblack 68; paraldehyde 148. 

Carbazotic acid, seepicric acid 18, and trinitrophenol 
205. 

Carbohydrates, menthol 129; naphthol 1386; resorcin 175; 
thymol 202. 

Carbolic acid, see phenol 144, 

Carbon, iniron, cupri-tetrammonium chloride 100. 

Carbon dioxide and carbonates, harium hydrate 51; 
calcium hydrate 64; tetrahydro-ellagic acid 89; mercuric chloride 
130; potassium hydrate 162; in potassium hydrate, calcium sulphate 
163; in beer, halimetric method, sodium chloride 185. 

Carbon disulphide and sulphocarbonates 66, 178; 
cobaltous nitrate 73; iodine 111; potassium hydrate, alcohol and 
cupric sulphate, yellow cuvrous xanthate 66; tri-ethyl phosphine 
204; zine sulphate 211. 

Carbon monoxide, cuprous chloride 98; cupric sulphate 
96; palladium 141, blood, or hemoglobin, spectrum 226. 

Cellulose, aniline sulphate 42; Schweitzer’s reagent, cupri- 
tetrammonium oxide 99; indol 110; iodine 111; phenol 144; zine 
chloride 210. 

Cerium salts 67. 

Chlorai hydrate 69; ammonium sulphide 38; aniline 40; 
naphthol 186; resorcin 175; silver nitrate 178. 

Chloric acid and chlorates, aniline sulphate 42; di- 
phenyl-amine 79; paratoluidine 148. 

Chlorine and chlorides 7%; volumetric, arsenic trioxide 45; 
cadmium iodide 61; blowpipe test, cupric oxide 95; lead aeetate 
119; mercurous nitrate 134; potassium didromate and sulphuric 
acid; chlorochromic acid; potassium iodide 165; silver nitrate 178; 
zinc iodide 210. 

Chloroform 71; aniline 40; naphthol 136; paraffin oil 142; re- 
sorcin 175; silver nitrate 178. 

Chromic acid and chromates 6; alcohol 26; aniline sul- 
phate 42; barium chloride 49; barium dioxide 50; hydrogen dioxide 
109; lead acetate 119; manganous sulphate 127; mercurous nitrate 


LIst OF TESTS, 285 


134; paratoluidine 148; silver nitrate 178; sodium diborate 186; 
sodium phosphate 192; carbazol 218. 

Chromium salts 72: ammonium sulphide 88; potassium ni- 
trate 166; sodium diborate 186; sodium phosphate 192; trimethyl- 
amine 204. 

Cinchona alkaloids 68, 73, 214; bromine, thalleioquine test 
59; chinoidine iodosulphate 68; chlorine 70: Prollius’ mixture, 
chloroform 71; ether 103; iodine, herapathite, 110; potassium hy- 
drate 162; potassium sulphate phocyanate 174; sodium salicylate 
194; zine chloride 210. 

Citric acid and citrates 6; barium acetate 48; calcium 
chloride 63. 


Coaltar dyes, tannic acid and sodium acetate 182; chloro- 
form 71. 

Cobalt salts 73; boracic acid 5; ammonium sulphide 88; ni- 
troso-beta-naphthol 136; potassium cyanide 158; potassium ferri- 
cyanide 161; potassium nitrite 167; potassium sulphocarbonate 173; 
potassium sulphocyanate, blue, spectrum 223; sodium diborate 
186; sodium pyrophosphate, electrolytic, 193; spectrum 223. 

Cocaine, see Alkaloids; potassium hydrate 162. 

Codeine, see alkaloids; iodic acid 11; molybdic acid 12; ammo- 
nium selenite 37; sodium hypochlorite 187. 

Codliver oil, carbon disulphide 66. 

Colchicine, see Alkaloids; ammonium metavanadate 37; 
sulphuric acid, yellow, nitric acid violet. 

Colocynthin, ammonium selenite 37; phenol 144; sodium se- 
lenate 194. 

Coloring in wine, chloroform 71; spectrum 227. 

Coniine, see Alkaloids; dry chlorine, purple, then blue, 
70. 

Copper and salts 90; hydrobromic acid 7; ammonia 30; am- 
monium benzoate 31; ammonium hyposulphite 35; ammonium sul- 
phocyanate 40; guaiacum 81; glucose 106; haematoxyline 85; iron 
112; potassium bromide 153; potassium cyanide 156; potassium fer- 
rocyanide 160; potassium sulphocyanate 174; sodium pyrophos-. 
phate, electrolytic, 198; sodium sulphite and pyrogallol 196; spec- 
trum 222. 

Coumarin, iodine, golden green. 

Cotton in woolen fabrics, alloxantin 28; Schweitzer’s test 99. 

Creasote, nitric acid, forms no picric acid; ferric chloride, 
green, 113; insoluble in glycerin, insoluble in ammonia. 

Creatine, trinitrophenol 205. 

Creatinine, trinitrophenol, 18, 205; sodium nitroprusside 191: 
zine chloride 210. 


286 LIST OF TESTS! 


~Curarine, see Alkaloids; bismuth-potassium iodide 56; po- 
tassium dichromate and sulphuric acid, blue, 157. 

Cyanogen and cyanides, aniline 40; guaiacum 81; ferric 
chlorlde 118; silver nitrate 178, sodium hyposulphite 189. 

Cystine, benzoyl chloride 212, 

Delphinine, see Alkaloids. 

Dextrin, cupric acetate 92. 

Dextrose, see glucose. 

Diazo-reaction, Ehrlich’s 20; see also safranine 177; sodium 
amalgam 182; naphthyl-amine 215. 

Didymium, spectrum 223. 

Digallic acid 23, see tannic acid. 

Digitalin, see Alkaloids and glucosides; phosphoric 
acid 17; chloral hydrate 69; zine chloride 210. 

Dimethyloxy-chinizine, see Antipyrine 44. 

Dinitro-cressol, zine, 208. 

Ehrlich’s diazo-reaction 20; see also safranine 177; so- 
dium amalgam 182; naphthyl-amine 215. ' 

Elaterin, ammonium selenite 37; phenol 144. 

Eosin, aluminium sulphate 29; fluorescence with alkalies; spec- 
trum 226. 

Erbium, spectrum 223. 

Ether, acetic, 101. 

Ether, ethylic, 102, 215; anthraquinone 43; paraffin oil 142; 
iodine 110. : 

Ether, nitrous, 139; antipyrine 44; potassium permangan. 
ate 169; potassium iodide and starch 165. 

Ethereal oils, hydriodic acid7; salicylic acid 19; chloral 
hydrate 69; fuchsine 80; cupric butyrate 92. 

Ethylene, cuprous chloride 93; fuming sulphuric acid 105; 
sulphur trioxide 200. 

Fehling’s test 97. 

Fermentation test, see Yeast 208. 

Ferric salts, see Iron salts. 

Ferricyanides, ferric chloride 113; ferrous sulphate 116. 

Ferrocyanides, cupric sulphate 96; ferric chloride 113; fer- 
rous sulphate 116; uranium acetate 205. 

Ferrous salts, see Iron salts. 

Fleitmann’s test for arsenic 14, 178, 208. 

Fluorine and fluorides, aniline 40; brazilwood 58; vola- 
tilization of silica, etching glass. | 

Formic acid and formates 25; ferric chloride 113; mer- 
curic chloride 180; silver nitrate 178. 

Fuchsin and other rosaniline derivatives 80; isonitril 


LIST OF TESTS. 237 


test chloroform 71; great solubility in fusel oil; sodium acetate and 
tannin 182; spectrum 227. 

Furfurol 105; Jorissen’s test, aniline 27, 41; urea 206; spec- 
trum 225. 

Fusel oil, seAmyl alcohol 26; methyl violet 85; conver- 
sion into valerianic acid by chromic acid 6, 157. 

Gallic acid 6; iodine 110; ferric chloride 113; ferrous sul- 
phate 116; lead acetate 120; potassium cyanide 158. 

Gallium, potassium ferrocyanide 160; spectrum 222. 

Gatehouse’s test for arsenic, se Aluminium 29. 

Geissler’s test for albumin, mercuric nitrate 133. 

Gelatin 106; tannic acid 23; galls 105; mercuric chloride 130; 
mercuric nitrate, red, 133. 

Gelsemine, sulphuric acid, red, then purple; nitric acid, 
green; ammonium metavanadate, purple, 35. 

Globulin, magnesium sulphate 127. 

Glucose 106; picric acid 18, 205; bismuth subnitrate, Boettger, 
Nylander 57; indigo, Mulder, 82; cupric acetate 92; cupric potas- 
sium carbonate, Soldaini, 93; cupric hydrate, Loewe, Haynes, 94; 
cupric sulphate, Trommer 96; cupric tartrate, Barreswill, Fehling» 
Degener, Pavy, Schmiedeberg,, 97; lead acetate 120; menthol, Mol- 
isch, 129; mercuric cyanide, Knapp, 131; mercuric potassium 
iodide, Sachse, 182; alpha-naphthol, Molisch, 136; nickel chloride, 
Mazzara, 137; nigrosin 177; phenyl hydrazine, Fischer, Schwartz, 
145; potassium hydrate, Heller, Moore, 162; resorcin 175; safranine, 
Crismer, 176; indulin 177; silver nitrate, Tollens, 178; thymol 202; 
stannous chloride 203; yeast 208. 

Glucosides, see Alkaloids and glucosides; Marme’s 
test 62; conversion into glucose by dilute acid, then glucose tests. 

Glycerin 28, 106; pyrogallic acid and stannic chloride 19, 203; 
phenol 144; sodium diborate 186. 

Godeffroy’s reagent, see silico-tungstic acid, 19. 

Gold and salts 107; oxalic acid 15; sulphurous acid 23; fer- 
rous sulphate 116; stannous chloride 203; spectrum 222. 

Griesmayer’s test, see tannic acid 23. 

Gurjun balsam 101, rose red, then violet with free mineral 
acids. 

Gutzeit’s arsenic test 8; see ferrous sulphide 117; magne- 
sium 124; phosphorus 147; silver nitrate 178; zine a 

Haematin, spectrum 226. 

Haemoglo bi n, spectrum 226. 

Halimetric method 185. 

Hardness of water, volumetric, soap solution 180, 181. 

Heller’s test for glucose, brown with potassium hydrate 162, 


238 LIST OF TESTS. 


Hofmann’s isonitril test 40. 

Hydrastine, ammonium metavanadate 35; ammonium sele- 
nite 27; potassium permanganate 169. 

Hydriodic acid7; see Iodine andiodides. 

Hydrobromic acid7; see Bromine and bromides. 

Hydrochloric acid 8; se Chlorine and chlorides. 

Hydrofluoric acid 9; see Fluorine and fluorides. 

Hydrofluosilicie acid 10; barium salts 48; potassium salts 
150. 

Hydrogen 108; palladium 140; platinum sponge, ignition, 149; 
spectrum 228. 

Hydrogen dioxide 109; titanic acid 24; potassium dichromate 
157; alpha-naphthyl-amine 215. 

Hydrogen sulphide 10, 110; para-amido-dimethy]l aniline 
21; chloral hydrate 69; lead acetate 119; silver nitrate 178; sodium 
nitroprusside and alkali 191. 

Hypochlorites 65, 164, 187; aniline 40; aniline sulphate 42; 
hydrochloric acid, chlorine; volumetric, sodium arsenite 65, 95; 
paratoluidine 143. 

Hyposulphites 189; iodine 110; ruthenium chloride 176; so- 
dium nitroprusside 191. : 

ITodic acid and iodates 11, 164, 190; tartaric acid 24; aniline 
sulphate 42. 

Iodine and iodides 110; nitric acid 14; nitrogen tetroxide 
14; osmic acid 15; tannic acid 23; ammonia 30; carbon disulphide 
66; chlorine 70; chloroform 71; cupric oxide, blowpipe test, 95; cu- 
pric sulphate 96; galls 105; lead acetate 119; mercuric chloride, 
volumetric, 130; mercurous nitrate 134; palladius chloride 141; 
palladious nitrate 142; silver nitrate 178; sodium hyposulphite, 
volumetric, 189; starch 198; thallous nitrate 201. 

Invert sugar, see Glucose. 

Iodoform, phenol-potassium 144; resorcin 175. 

Tridium 112; ammonium chloride 82. 

Iron and salts 112; gallic acid 6; tannic acid 23; ammonia 
30; ammonium succinate 38; ammonium sulphide 38; ammonium 
sulphocyanide 40; antipyrine 44; galls 105; nitroso-beta-naphthol 
136; potassium ferrocyanide 160; potassium ferricyanide 161; po- 
tassium permanganate 168; potassium sulphocyanate 174; resorcin 
175; sodium acetate 182; sodium pyrophosphate, electrolytic, 193; 

Isonitril test 40, 71. 

Jorissen’s test for furfurol, aniline 40. 

Kakodyl test for arsenic and acetates 45. 

Ketones, hydroxylamine 110; phenyl-hydrazine 145. 

Kjeldahl’s method for organic nitrogen, fuming sulphuric 


LIST OF TESTS. 239 


acid 105; phosphorus pentoxide 147; potassium permanganate 169; 
sulphur trioxide 200. 
Krammato method 389. 


Lead and salts 118; hydrochloric acid 8; hydrogen sulphide 
10; sulphuric acid 21; cochineal 77; potassium dichromate 157; po- 
tassium iodide 165; im sulphate 172; Asse um 222. 

Lieben’s iodoform test 110. 


Lignin, aniline sulphate 42; tetramethyl-paraphenylene-dia- 
mine 48; indol 110; phenol 144; potassium hydrate 162. 


Lithium salts, amyl alcohol 29; ether 102; potassium stan- 
nous chloride 171; spectrum 220. 


Magnesium and salts 124; ammonia 30; ammonium car- 
bonate 31; ammonium chloride 32; ammonium phosphate 87; bar- 
ium acetate 48; mercuric oxide 134; soap solution 180; sodium 
phosphate 192; spectrum of metal 221; with purpurin 221. 

Malic acid and malates, calcium chloride 63; potassium 
dichromate 157. 

Marganese salts 127; oxalic acid 15; ammonium sulphide 
38; volumetric, bismuth tetroxide 57; sodium carbonate, blowpipe, 
184; sodium diborate, blowpipe, 186; sodium pyrophosphate, elec- 
trolytic, 193; spectrum, manganous chloride, 222. See also perman- 
ganates. 

Meconic acid, iodine 110; ferric chloride 113. 

Menthol 128. 

Mercury and salts 128; hydrochloric acid 8; hydrogen sul- 
phide 10; sulphurous acid 23; copper 91; gold 107; potassium chrom- 
ate 156; potassium iodide 165; sodium pyrophosphate, electrolytic, 
198; stannous chloride 208. 

Metals , see bases, metallic. 

Metaphosphoriec acid 17, albumin 25; for other tests see 
phosphoric acid. 

Molybdic acid and derivatives 12, 190; hydrogen di- 
oxide 109; potassium ferrocyanide 160; zinc and acid, blue, 208. 


Morphine, see alkaloids; iodic acid 11; sulpho-molybdic acid, 
Froehde, 12; mire acid 14; titanic acid 24; cupri-tetrammonium 
sulphate, green on boiling, Nadler’ s test; ine 110; ferric chloride 
118; ferric ferricyanide 115; methylene Ee eehiscivdrin 136; po- 
tassium iodate 164; sodium arsenate 183; sodium hypochlorite 187; 
cane sugar 199. 

Naphthalin red, spectrum 225. 

Naphthol 136; chloral hydrate 69; chloroform 71. 

Narceine, see alkaloids; chlorine, then ammonia, red, 70; fer- 
ric chloride 113; zine chloride 210; zinc iodide and iodine, blue, 210. 


940 LIST OF TESTS. 


Narcotine, see alkaloids; sulpho-molybdie acid 12; ammo- 
nium metavanadate 35. 

Nickel and salts 137; ammonium sulphide 88; bromine 59; 
chlorine 70; potassium cyanide 158; potassium nitrite 167; potas- 
sium sulphocarbonate 173; sodium pyrophosphate, electrolytic 193; 
sodium sulphide, volumetric, 195. 

Nicotine, see alkaloids. 

Nitric acid and nitrates 14; pyrogallic acid 18; alumi- 
nium 29; aniline sulphate 42; brucine 60; cinchonamine 73; diphenyl- 
amine 79; indigo 82; copper 91; ferrous sulphate 116; paratolui- 
dine 148; phenol 144; potassium stannous sulphate, volumetric, 171; 
potassium sulphocyanate 174; carbazol 213. 

Nitrobenzol, reduce by nascent hydrogen and test for ani- 
line; potassium hydrate, green, 162. 

Nitrogen in organic Sherer Kjeldahl’s method, 105, 147, 
169, 200; potassium 162. 

Nitroprussides 168, 191; ammonium sulphide 38; potassium 
sulphide 173; sodium sulphide 195. 

Nitrous acid and nitrites 167, 179, 191; meta-di-amido- 
benzoic acid 12; pyrogallic acid 18; sulphanilie acid and alpha- 
naphthyl-amine 20, 215; aniline 40; antipyrine 44; cadmium iodide 
61; metaphenylene-diamine 78; fuchsin 80; phenol 144; potassium 
iodide 165; potassium sulphocyanate 174; urea, azotometric, 206; 
zinc iodide 210. 

Nitrous ether 139; antipyrine 44; potassium permanganate 
169. . 

Oil dipterocarpus 101; free mineral acids 101. 

Oil lemon, cupric butyrate 92. 

Oil peppermint, salicylic acid 19. 

Oil turpentine, cupric butyrate 92; iodine 101; oil poppy 
139. 

Oils, iodine addition number 111; sodium nitroprusside 191. 

Olefiant gas, sulphur trioxide 200. ¢ 

Olefines, Allen’s solution, sodium hypobromite 180. 

Organic matter in water, potassium permanganate 169. 

Ortho-phosphorie acid, see phosphoric acid 17. 

Osmic acid 165. 

Oxalic acid and oxalates 15; calcium chloride 63; cal- 
cium sulphate 66; potassium permanganate, volumetric, 168. 

Oxygen 139; pyrogallic acid 18; chromous chloride 72; cu- 
prous chloride 93; phosphorus 146; sodium hydrosulphite 189. 

Ozone, aniline 40; para-amido-dimethyl-aniline 43; guaiacum 
81; Wurster’s papers 43, 90; potassium iodide 165; thallium paper 
202; zinc iodide 211. 


LIST OF TESTS. 241 


Palladium and salts 140; hydrogen 109, 140; iodine 110; 
potassium bromide 153; potassium iodide 165. 

Perchloric acid and salts 16; potassium salts 150 ff. 

Permanganates 168; oxalic acid 15; aniline sulphate 42; fer- 
rous sulphate 116; paratoluidine 148; potassium tetroxalate 168; 
spectrum 223. 

Phe nacetine, potassium nitrite 167. 

Phenol 144, nitric acid 14; bromine 59; ferric chloride 113; 
mercurous nitrate 134; nitrous ether 139; potassium bromate and 
bromide 152, 158; potassium nitrite 167; sodium bromate 188. 

Phosphine, cuprous chloride 938; silver nitrate, black, 178. 

Phosphoric acid and phosphates 17, 192; ammonium 
molybdate 18; ammonium citrate 33; luteo-cobaltic chloride 75; 
magnesium chloride 125; magnesium sulphate 127; sodium acetate 
182; sodium oxalate 192; uranium acetate 205; uranium nitrate 
205. - 

Picric acid 18, 205; glucose 106; potassium cyanide 158; zinc 
208. 

Piperine, see alkaloids, ammonium metavanadate 35. 

Platinum and salts 148; ammonium chloride 32; potassium 
salts 150 ff.; stannous chloride reduces brown platinic to red plati- 
nous chloride, 208. 

Potassium and salts 150; hydrofluosilicie acid 10; perchloric 
acid 16; tartaric acid 24; ammonium fluoboride 34; bismuth sodium 
hyposulphite, Campari, 57; sodio-cobaltic nitrite 75; platinic chlor- 
ide 149; sodium acid tartrate 196; spectrum 220. 

Ptomaines, ferric ferricyanides 115. 

Pyridine bases, methyl iodide 135. 

Pyrogallic acid 18; nitric acid 14; iodine 110; ferric chlor- 
ide 118; potassium hydrate 162. 

Pyro-phosphoric acid 17, 198; see phosphoric acid; luteo- 
cobaltic chloride 75. 

Quinine, see cinchona alkaloids. 

Quinone, hydrocoerolignone 108. 

Racemie acid » calcium chloride 63. 

Rhodanates, see sulphocyanates, 40, 170. 

Rosaniline derivatives, isonitril test, chloroform 71; spec- 
trum 227. 

Rubidium salts, sodio-cobaltic nitrite 75; platinic chloride 
149; spectrum 220. 

Ruthenium salts 176. 

Saccharin, resorcin 175. 

Saffron, oil almond dissolves color, 189. 

Safranine 176; sulphuric acid 176; spectrum 225. 


242 LIST OF TESTS, 


Salicin, sulphuric acid, red, 21; potassium dichromate and 
sulphuric acid, spiraea odor, 157. 

Salicylic acid and salicylates 19, 88, 194; alcohol 27; 
ferric chloride 118; cupric sulphate, green; nitrous ether 139. 

Santonin, ferric chloride and sulphuric acid, red, 113; zine 
chloride 210. 

Selenates and selenites 87, 194; ferrous sulphate 115. 

Silicic acid and silicates 19; hydrofluoric acid 9; blow- 
pipe test, skeleton, microcosmic salt 198. 

Silk, zine chloride 210. 

Silver and saltsi1%77; hydrochloric acid 8; hydrogen sul- 
phide 10; sulphurous acid 28; formic acid 25; ammonia 80; ammo- 
nium sulphide 88; ammonium sulphocyanate, volumetric, 40; hy- 
droxylamine 110; iodine 110; potassium hydrate 156: potassium 
cyanide 158; potassium iodide 165; sodium chloride, volumetric, 
185, 186; sodium hyposulphite 189; sodium pyrophosphate, electro- 
lytic, 193. 

Sodium and salts 181; potassium acid pyroantimonate 
170; potassium stannous chloride 171; uranium acetate, micro- 
scopic, 205; spectrum 220. 

Solanine, see alkaloids; sulphuric acid and alcohol, red. 

Stannic and stannous salts, see tin. 

Starch 198; diastase 100; iodine 110; potassium hydrate 162. 

Strontium salts 198; ammonium sulphate 38; calcium sul- 
phate 66; potassium chromate 156; potassium dichromate 157; po- 
tassium sulphate 172; spectrum 221. 

Strychnine, see alkaloids; chromic acid 6; perchloric acid 
16; ammonium metavanadate 35; cerium dioxide 67; red lead 123; 
potassium dichromate 157; potassium permanganate 168; sodium 
selenate 194; sodium metatungstate 194; zine chloride 210. 

Succinates 88; ferric chloride 113. 

Sugar 106, 199; see cane sugar and glucose. 

Sulphocyanates 40, 174; ferric chloride 113: 

Sulpho-haemoglobin, spectrum 226. 

Sulphur and sulphides, 10, 38, 52,110, 117, 127, 178, 195, 
200, —; para-amido-dimethyl-aniline 43; hydrogen dioxide 109; 
lead acetate 119; potassium cyanide 158; silver 177; silver nitrate 
178; sodium nitroprusside 191. 

Sulphuric acid and sulphates 21; barium salts 38; lead 
acetate 119; sodium carbonate, blowpipe, hepar test; strontium 
chloride, volumetric, 198; sugar 199. 

Sulphurous acid and sulphites 28; ferric chloride 113; 
mercurous nitrate, blackened, 134; sodium nitroprusside 191; re- 
duction by zine 208. 


LIST OF TESTS. 243 


Tannic acid 23: albumin 25; chlorine water and ammonia, 
red, 59; chromic alum 172; gelatin 106; iodine 110;. ferric 
acetate 118; ferric chloride 113; ferrous sulphate 116; lead ace- 
tate 119; lead hydrate 123; nickel sulphate, volumetric, 188; po- 
tassium permanganate, volumetric, 169; potassium antimonous 
tartrate, volumetric, 174; cinchonine 214. 

Tartaric acid 24; calcium chloride 63; potassium acetate 151. 

Textile fabrics, alloxantin 28; cupri-tetrammonium hydrate 
99; zine chloride 210. 

Thalline, ferricchloride 113. 

Thallium salts 201; platinic chloride 149; potassium iodide 
165; spectrum 221. 

Thebaine, see alkaloids; zinc chloride 210. 

Tin and salts 202; gold chloride 107; mercuric chloride 1380; 
spectrum 222. 

Titanic acid 24; barium dioxide 50; hydrogen dioxide 109. 

Trinitrophenol 18, 205; see picric acid. 

Uranium salts 205; phosphoric acid 17, 205; ammonium 
carbonate 31, 205; ammonium sulphide 38, 205; potassium ferrocy- 
anide 160, 

Urea 206; bromine 59; caleium hypochlorite 65; furfurol 105; 
mercuric nitrate, volumetric, 183; potassium hypochlorite 164; so- 
dium hypobromite, azotometric, 187; sodium hypochlorite 187; ni- 
trites 191, 205; spectrum 225. 

Uric acid and urates, nitric acid, murexid test, 14; am- 
monium sulphate 38. 

Vanadic acid and vanadates 35; tannic acid 28; ani- 
line sulphate 42; hydrogen dioxide 109. 

Veratrine, see alkaloids; zine chloride 210. 

W ater 207; anthraquinone 43; calcium chloride 63; cupric sul- 
phate, anhydrous, 96; paraffin oil 142; hardness, soap solution, 180. 

Wine adulterations, chloroform 71; spectrum 227. 

Wood pulp in paper, see lignin; aniline sulphate 42: 
phenol 144; potassium hydrate 162. 

W ool, alloxantin 28. 

Zine and salts 208ff.; formic acid 25; ammonium sulphide 
38; cobaltous nitrate, blowpipe, 73; potassium cyanide 158; sodium 
pyrophosphate, electrolytic, 193; sodium sulphide, volumetric, 195. 


GEO G HiGHCOCK 


RELATIONS OF METRIC TO U. S. MEASURES AND WEIGHTS. 


The metric wnit of length is obtained by dividing the distance 
from the earth’s equator to the pole into 10,000,000 parts. Itis 
called the Metre and corresponds to 30.37079 English inches, ac- 
cording to the standard of conversion authorized by the U. S. 
Congress and by the British Parliament. (Clarke’s correction, 1 
metre = 89.3870482 inches, has been adopted by the U. 8. Pharma- 
copeia.) 

It is subdivided and multiplied, as follows: 

1 Metre = 10 decimetres = 100 centimetres = 1000 milli 
metres. 

1000 metres = 1 kilometre = 10 hektometres—100 dekametres. 

1 inch = 25.3995 millimetres. 

1 foot = 304.794 millimetres. 

1 cubic decimetre is the wnit of volume, 
called the litre, and equals 1000cubie centi- 
metres (Ce.) or millilitres. 

1 litre = 83.81 fluid ounces = 2.1185 pints = 
0.26419 gallons, wine measure (= 1.76 pints 
imperial measure). 

1. millilitre =1 cubie centimetre = 16.25 
minims. 

1 minim = 0.06 Ce.; 1 fluid ounce = 29.58 Ce. ; 
1 pint = 473.148 Ce.; 1 gallon (wine measure) 
= 8785.15 Ce. 

The unit of weight is called the gramme 
(gr.). It is the weight of 1 cubic centimetre 
of water at 4° C., its point of greatest density. 

The gramme is subdivided and multiplied, 
as follows: 

1 gramme = 10 decigrammes = 100 centi- 
grammes = 1000 milligrammes. 

4/006 grammes —1 kilogramme = 10 hekto- 
grammes = 100 dekagrammes. 

1 Cc. water weighs 1 gr.; 1 litre water 
weighs 1 kilogr. 

1 gramme = 15.43234874 grains troy. 

1 kilogramme = 2.6803 pounds troy = 
2.20462 pounds avoirdupois. 

1 grain troy = 64.799 milligrammes. 

1 pound ayoirdupois = 453.6 grammes. 

1 gramme per litre = 58.329 grains troy per wine gallon (= 70 
grains troy per imperial gallon). 


100 MILLIMETRES. 


0 
LJ 
I 
O 
3 


10 CENTIMETRES 


ENGLISH 


! DECIMETRE 





TNG LA 


A 
Absolute alcohol, 27 
Absolute ether, 102 
Absorption spectra, 223 
Acetanilide, 42 
Aceticacid, 5 
Acetic ether, 101 
Acetoximes, 110 
Acids— 
acetic, 5 
aniline-parasulphonic, 20 
arsenous, 45 
aurochloriec, 107 
benzol-meta-disulphonic, 175 
boracic or boric, 5, 9 
carbazotic, 18, 205 
carbolic, 144 
carminic, 77 
chloro-platinic, 149 
chromic, 6, 23 
citraconic, 73 
citric, 6 
diazobenzol-sulphonic, 20 
digallic, 23 
dimethyl - amido - azobenzol 
sulphonic, 78 
eupittonic, 80 
formic, 25 
fuming nitric, 14 
fuming sulphuric, 105 
gallic, 6 
hydriodic, 7 
hydrobromice, 7 
hydrochloric, 8 
hydrofluoboric, 34 
hydrofluoric, 9 
hydrofluosilicic, 10 
hydrosulphuric, 10, 21, 52, 110 


iodic, 11 
meta-diamido-benzoic, 12 
meta - dioxy -azobenzol - sul- 
phonie, 89 
meta-phosphorie, 17 
meta-tungstic, 12 
meta-wolframic, 12 
molybdie, 12 
nitric, 14, 18 
nitro-hydrochlorie, 15 
nitro-muriatic, 15 
nitro-prussic, 168, 191 
ortho-phosphorie, 17 
osmic, 15 
oxalic, 15 
oxy-azobenzol sulphonic, 89 
para-rosolic, 19 
perchloric, 16 
perosmic, 15 
phenyl-amido-azobenzol-sul- 
phonic, 89 
phosphoric, 17, 13 
phosphoric glacial, 17 
phospho-antimonie, 17 
phospho-molybdie, 12 
phospho tungstic, 18 
phospho-wolframic, 18 
picric, 18, 205 
pyrogallic, 18 
red fuming nitric, 14 
rosolic, 19 
salicylic, 19, 88, 194 


 selenic, 194, 116 


selenous, 37 
silicic, 19, 9 
silico-tungstic, 19 
sulphanilic, 20 
sulphydric, 10 


246 


sulpho-molybdie, 12 
sulphuric, 21 
sulphuric, anhydrous, 200 
sulphuric, fuming, 105 
sulphurous, 23 
tannic, 23, 182 
tartaric, 24 
tetra-hydro-ellagic, 89 
titanic, 24 
trichloraeetic, 25 
uric, 14 
vanadic, 35, 23 
Aconitine, 17, 56 
Albumin, 25, 17, 18, 23, 25, 168, 
197, 205 
Alcohols, 26 
amyl, 26 
ethyl, 27, 6 
glycerin, 28, 107, 19 
propenyl, 28 
Aldehyde, 20 
Alkalies, tests for, see test papers 
and color reagents, 76ff 
Alkaline hydrates, 23 
Alkaloids, tests for, 6, 11, 12, 14, 
16, 18, 23,; see list of tests p. 
Allen’s volumetric solution, 189° 
Alloxantin, 28 
Alpha-naphthol, 136 
Alpha-naphthyl-amine, 215 
Alum, 29 
Aluminium, 29 
Aluminium sulphate, 29 
Aluminium salts and purpurin, 
spectrum, 221 
Amalgams, 29 
Amalgam, copper, 91 
Amalgam, sodium, 182 
Amianthus, 46 
Amido-benzol, 42 
Amido-dimethyl-aniline, 43 
Ammonia and ammonium com- 
pounds, 30 
Ammonia, 30, 8, 19 


, 


INDEX. 


Ammonia water, 30 
Ammonium benzoate, 31 
borofluoride, 34 
carbonate, 31 
chloride, 32 
citrate, 33 
fluoboride, 34 
hydrate, 30 
hydrogen fluoride, 34 
hyposulphite, 34 
magnesium citrate, 33 
meta-vanadate, 35 
nitrate, 36 
oxalate, 36 
phosphate, 37 
polysulphide, 38 
rhodanate, 40 
selenite, 37 
sodium phosphate, 193 
succinate, 38 
sulphate, 38 
sulphydrate, 38 
sulphide, 38 
sulphocyanate, 40 
thiocyanate, 40 
thiosulphate, 30 
Aniline compounds, 40 
Aniline, 40, 161 
sulphate, 42 
 amido-dimethyl aniline, 43 
amido-benzol-azo - dimethyl- 
aniline, 43° 
p methyl aniline, see p tolui- 
dine, 143 
Anthraquinone, 43, 189 
Antifebrine, 42 
Antimonous potassium tartrate, 
174 
Antipyrine, 44 
Aqua ammonie, 30 
fortis, see nitric acid, 14 
regia, see nitro muriatic acid, 
15 


) Arsenic, tests for, see list of tests 


INDEX. 247 


Arsenic trioxide, 45 subnitrate, 57 
Asbestus, 46, 95 tetroxide, 57 
Aspidospermine, 16 thiosulphate, 57 
Assay reagents, 47 Black flux, 104 
Assay ton, 119 Bleaching powder, 65 
Atomic weights, 3 Blood spectra, 225 
Atropine, 18 Boettger’s test, 57 
Auric chloride, 107 ; spectrum, 222) Bohlig’s reagent, 131 
Aurin, 19 Boracice acid, 5 
Aurochloric acid, 107 Borax, 186 
Azolitmin, 47 Brass, 58 


Brazilin, 58 , spectrum, 224 


5 Brazilwood, 58 
Barium compounds, 48 Bromine, 59 
acetate, 48 Bromine water, 59 
boro-tungstate, 61 Bromoform, 60 
carbonate, 48 Brucine, 60, 14, 16, 18 
chloride, 49 
dioxide, 50 Cc 
hydrate, 51 Cabbage, red, 77 
mercuric iodide, Rohrbach’s | Cadmium compounds, 61 
solution, 52 boro-tungstate, 61 
nitrate, 52 chloride, 213 
spectrum, 221 iodide, 61 
sulphide, 52 potassium iodide, 62 
Barreswill’s solution, 99 spectrum, 222 
Baryta water, 51 Caesium stannous chloride, 203 
Beer, halimetric method, 185 Caffeine, 18 
Benzene, see benzol, 54 Calcined magnesia, 126 
Benzin, 53 Calcium compounds, 62, 15 
Benzol, 54 carbonate, 62 
Benzol-meta-disulphonic acid, 175 chloride, 63 
Benzol-sulphon-diazide, 20 fluoride, 64 
Benzo purpurin, B., 77 hydrate, 64 
Benzoyl chloride, 212 hypochlorite, 65 
Beryllium potassium hydrate, 162 spectrum, 221 
Bettendorff’s arsenic test, 202, 203 sulphate, 66 
Bile acids, 199 Campari’s reagent, 57 
Bile colors, 20 |Caramel, 66 
Bilirubin, 20 Carbazol, 213 
Bismuth compounds, 55 Carbazotic acid, 18, 205 
hydrate, 55 Carbolic acid, 144 
potassium iodide, 56 Carbon dioxide, 214; in beer, 185 


sodium hyposulphite, 67 © / Carbon disulphide, 66 


248 


Carbon monoxide, in blood, spec- 
trum, 226 
Carmine red, spectrum, 224 
Carminic acid, 77 ; spectrum, 224 
Cerium dioxide, 67 
hydrate, 67 
Charcoal, 68 
Chinoidine iodosulphate, 68 
Chloral alcoholate, 69 
Chloral hydrate, 69 
Chlorine, 70 
Chlorine water, 70 
Chloroform, 71 
Chlorophyll, spectrum, 228 
Chromium compounds, 72 
Chromic acid, 6, 23 
alum, 72 
sulphate, 72 
Chromous chloride, 72 
Chrysoin, 89 
Cinchonamine, 73 
Cinchonine, 214 
Citraconic acid, 73 
Citric acid, 6 
Cobalt compounds, 73, 161 
cobaltous nitrate, 73 
luteo-cobaltic chloride, 75 
paper, 75 
purpureo-cobaltic chloride,74 
sodio-cobaltic nitrite, 75 
sulpho-cyanate, spectrum, 223 
Cochineal, 77, 29 
Codeine, tests for, 11, 12, 164, ete. 
see list of tests. 
Coleus Verschaffelti, 77 
Cologne spirit, 27 
Color reagents and indicators, 76 
Congo red, 77 
Copper and its compounds, 90 
copper, metal, 90 
cuprammonium comp’ nds, 99 
cupri-tetrammonium chlo- 
ride, 100 
hydrate, 99 


INDEX. 


sulphate, 99 
cupric acetate, 92 
basic, 92 
butyrate, 92 
potassium carbonate, 93 
hydrate, 94 
oxide, 95 
subacetate, 92 
sulphate, 96 
tartrate, 97 
Barreswill’s solution, 99 


Degener’s sis 99 
Fehling’s cpa dt, 
Pavy’s oe oes 
Schmiedeberg’s ‘‘ 99 


cuprous chloride, 93 
spectrum, 222 

Corallin, 19, 29 
Creatinine, tests for, 191, 205 
Cupric salts, see copper. 
Cuprous salts, see copper. 
Curcuma, 89 
Curcumin, 89 
Curcumin W., 78 
Cyanin, 79 


Dahlia, 81 

Dead oil, 145 

Degener’s solution, 99 

De Vrij’s reagent, 12 

Dextro-glucose, 106 

mDiamido-benzol, 78 

mDiamido-benzoic acid, 12 

Diastase, 100 

Diazobenzol-sulphonic acid, 20 

Didymium, spectrum, 223 

Digallic acid, 23 

Digitaline, 17, 69 

Dimethyl- amido - azobenzol - sul- 
phonic acid, 78 

Dimethyl - para- phenylene - dia- 
mine, 43 


| Dimethyl-oxy-chinizine, 44 


’ INDEX, : 249 


Diphenyl-amine, 79 Fleitmann’s test, 14, 178, 208 
blue, spectrum, 227 Fluorescein, 80 
orange, 89 Fluorspar, 64 
Dipterocarpus oil, 101 Fluxes, 104: 
Docimastic reagents, 47 Free acids, 6, 19, 47, 76ff, see list 
Dragendorfi’s reagent, 56 of tests. 
E Fresenius and Will’s method, 127 
Froehde’s reagent, 12, 190 
Ehrlich’s diazo-reaction, 20 Fron’s reagent, 56 
Elderberries, spectrum, 227 Fuchsin, 80, 29 
Emission spectra, 219 paper, 81 
Eosin, 79, 29; spectrum, 225 spectrum, 227 
Epsom salt, 127 Fuming sulphuric acid, 105 
Erbium spectrum, 223 Fuming nitric acid, 14 
Erdmann’s reagent, 21 Furfurol, 105, 206 
Ethereal oils, 7, 19, 92 Jorissen’s test, 27, 41 
Ethers, 101, 102 spectrum, 225 
Ethyl acetate, 101 urea, 206 
Ethylic ether, 102, 215 Fusel oil, 26 
Ethyl nitrite, 139 
Ethyl orange, 80 C 
Eupittonic acid, 80 Gallein, 81 
F Gallic acid, 6 
Galls, 105 

Faisst and Knauss’ table of hard- | Garnet, 47 

ness of water, 181 Gatehouse’s arsenic test, 29 
Fehling’s solution, 97 Geissler’s test, 133 


Fermentation test, see yeast, 208 | Gelatin 106, 23 
Fernambuco, see Brazilwood, 58 | Gentiana violet, 81 


Ferric acetate, 113 Glass, 104 
alum, 115 Glasswool, 47 
chloride, 113 Glucose 106, 18 
dinitrosulphide, 115 Glycerin 28, 106, 19 
ferricyanide, 115 Godeffroy’s reagent, 19 
oxide, 115 Gold 107, 23 
salts, 25 f chloride, 107 
sulphate, 115 spectrum, 222 
Ferrous chloride, 115 Gray flux, 104 
potassium oxalate, 117 Griess’ reagent 20, 215 
sulphate, 116 Griesmayer’s test, 23 
ammonium sulphate, 116 Guaiacum, 81 
salts, 6, 23 paper, 81 
sulphide, 117 tincture, 81 


Flavescin, 80 Gurjun balsam, 101 


250 


INDEX. 


: 


Gutzeit’s arsenic test,8, 117, 124, | Iodine, 110, 14, 15, 23 


147, 178 
Gypsum, 66 


H 

Haematin, 226 

spectrum, 226 

with C O, 227 
Haematoxylin, 84 
Haemin, 225 
Haemoglobin, 225 

spectrum, 226 

with C O, 226 
Halimetric method, 185 
Harada’s separating funnel, 61 
Hardness of water, 180 
Haswell’s titration process, 203 
Haynes’ solution, 95 
Helianthin, 20 
Heller’s glucose test, 162 


Hofmann’s chloroform test, 41, 71 


Hydriodie acid, 7 
Hydrobromic acid, 7 
Hydrochloric acid, 8 
Hydrocoerolignone, 108 
Hydrofluoric acid, 9 
Hydrofluosilicic acid, 10 
Hydrogen, 108 
Hydrogen dioxide, 109 


Hydrogen sulphide, 10, 52, 110, 


127, 21 
Hydrorufigallic acid, 89 
Hydrosulphurie acid, 10, 52, 110 
Hydroxylamine, 110 


i 

Indicators, 76 

Petri and Lehmann’s, 86 
Indigo, 82 
Indigotin, 82 
Indol, 110 
Indulin, 177 
Iodie acid, 11 


Todides, 14, 15, 56, 61, 131, 135, 141, 


165, 200, 210 


addition number, 111 
cyanide, 11) 
pentoxide, 111 
Iodoform test, Liebens’, 110 
Iridium sodium chloride, 112 
Iron and its compounds, 112 
ferric acetate, 113 
alum, 115 
chloride, 113 
dinitrosulphide, 115 
oxide, 115 
salts, 23, 160 
sulphate, 115 
ferrous chloride, 115 
potassium oxalate, 117 
salts, 161 
sulphate, 116 
ammonium sulphate, 116 
sulphide, 117 
Isinglass, see gelatin, 106 


J 
Jorissen’s test, 27, 41 


K 


Kakody] test, 45 
Kaolin, 118 

Kieffer’s reagent, 99 
Kieselguhr, 47 

Klein’s reagent, 61 
Knapp’s solution, 131 
Krammato method, 58 
Kryolite, 118 


L 


Lacmoid, 83 
Lacmus, 84 
Lead and its compounds, 118 
acetate, 119 
carbonate, 121 
chloride, 121 
chromate, 122 
dioxide, 123 


INDEX. 


hydrate, 123° 
monoxide, 122 
nitrate, 122 
oxides, 122 
red, 123 
spectrum, 222 
subacetate, 120 
Liebig’s volumetric solution, 133 
Lime, 64 
water, 64 
Liquor Dzondii, 31 
Litharge, 122 
Lithium chloride, 26 
spectrum, 220 
Litmus, 84 
Loewe’s solution, 94 
Logwood, 84 
Luchini’s reagent, 157 
Lustgarten’s reagent, 136, 69, 71 
Luteo--cobaltic chloride, 75 


Magnesia mixture, 125, 127 
Magnesium and its compounds, 
124 
chloride, 125 
hydrate, 126 
hydrosulphide, 127 
oxide, 126 
spectrum, 221 
with purpurin, 221 
sulphate, 127 
sulphide, 127 
Malva, 85 
spectrum, 227 
Mandarin, 89 
Mandelin’s test, sulpho-vanadic 
acid, 35 
- Manganese compounds, 127 
dioxide, 127 
manganous chloride, 
trum, 222 
sulphate, 128 
Marme’s reagent, 62 


spec- 


251 


Marsh’s arsenic test, 8, 45, 91 
Mayer’s solution, 132 
Menthol, 128 
Mercury and its compounds, 128 
mercuric chloride, 129 
cyanide 131 
iodide, 181. 
nitrate, 133 
- oxide, 134 
oxychloride, 130 
potassium iodide, 131 
mercurous nitrate, 134 
salts, 8 
Mesityl-quinone, 85 
Meta-chloral, 69 
Meta-diamido-cenzol, 78 
Meta-dioxy-azobenzol-sulphonic 
acid, 89 
Meta-dioxy-benzol, 175 
Meta-phenylene-diamine, 78 
Meta-phosphorie acid, 17 
Meta-tungstic acid, 12 
Methaemoglobin, spectrum, 225 
Methyl aurin, 19, 
Methyl iodide, 135 
Methyl orange, 78 
Methyl violet, 85 
Methylene aceto-chlorhydrin, 136 
Methylene blue test for hydrogen 
sulphide, 43 
Methylene iodide, 135 
Millon’s test, 133 
Molisch’s test, 128, 136 
Molybdenyl sulphate, 12 
Molybdic acid, 12 
Moore’s glncose test, 162 
Morphine, 11, 12, 164, 190 
Mulder’s glucose test, 82 


Naphthalin red, spectrum, 225 
Naphthameine, 216 
Naphthol, alpha, 136 

beta 136 





252 


Naphthyl-amine, alpha, 20, 215 
Narcotine, 12 
Nessler’s test, 86, 132, 133 
Nickel and its compounds, 1387 
Nickelous chloride, 137 
hydrate, 138 
oxalate, 138 
oxide, 138 
sulphate, 139 
Nigrosine, 177 
Nitric acid, 14, 18 
Nitrites, 12, 18, 20, 40, 44, 78 
Nitrogen tetroxide, 14 
Nitro-phenol, para-, 86 
Nitroso-beta-naphthol, 186 
Nitrous acid, 12, 18, 20, 40, 44, 78 
Nitrous ether, 139 
Nylander’s solution, 57 


oO 


Oil almond, 139 
dipterocarpus, 101 
light, 54 
linseed, 139 
peppermint, 19 
poppy 189 
vitriol, 22 

Olefiant gas, 200 

Olefines, 189 

Orange I, 89 
II, 89 
III, 21, 78, 89 
peel, 86 

Ortho-phosphorie acid, 17 
toluidine, 41 

Osmic acid, 15 

Osmium tetroxide 15 

Oxalic acid, 15 

Oxy-azobenzol-sulphonic acid, 89 

Oxygen, 18, 139 

Oxyhaematin, 226 

Oxyhaemoglobin, 225 

Oxy-naphthyl-amine, 216 


INDEX. 


p 


Palladium and its compounds, 140 

palladious chloride, 141 

nitrate, 142 
palladium asbestus, 46, 140 
paper, 141 

Paper, cabbage, 77 

cobalt, 75 

congo, 77 

dahlia, 81 

fuchsin, 81 

georgina, 81 

guaiacum, 81 

litmus, 84 

palladium, 141 

phenol-phthalein, 87 

test, 88 

thallium, 202 

turmeric, 89 

Wurster’s, 43, 90 
Para-amido-dimethyl-aniline, 21, 
Para-amido-tetramethyl-aniline, 


’ 


Paraffin, 142 

Paraffir’ oil, 142 

Paraldehyde, 143 

Para-nitro-phenol, 86 

Para-rosolic acid, 19 

Para-toluidine, 42, 143 

Pavy’s solution, 99 

Pentamethyl-parafuchsin, 85 

Perchlorie acid, 16 

Permanganates. 15, 168, 223 

Pernambuco wood, 58 

Perosmic acid, 15 

Petri and Lehmann’s indicator, 86 

Petroleum ether, 53 

Phenacetolin, 86 

Phenol, 144 

Phenol-phthalein, 87 

Phenol-potassium, 145 

Phenyl-amido-azobenzol-sulpho- 
nic acid, 89 


Phenylene-diamine, meta, 78 
Phenyl-hydrazine, 145 
Phloroglucin, 87 
Phospho-antimonic acid, 17 
Phosphoric acid, 17, 13 
Phospho-tungstic acid, 18 
Phospho-wolframic acid, 18 
Phosphorus, 146 

Phosphorus pentoxide, 17, 147 
Picric acid, 18, 205 

Plaster of Paris, 66 


INDEX, 253 


bromide, 153 
carbonate, 153 
chlorate, 155 
chromate, 156 
copper carbonate, 93 
copper cyanide, 160 
cyanide, 158 
dicarbonate, 155 
dichromate, 157 
disulphate, 173 
ferri-cyanide, 161 


Platinum and its compounds, 148 
Plate i, polariscope, 106 


ia9 


iad 


li, volumetric instrum’ts, 52 

iii, Kipp’s, Marsh’s, Fleit- 
mann’s app., 117 

iv, gas burette and pipette, 93 

v, Fehling’s, Harada’s app., 


ferro-cyanide, 160 
ferrous oxalate, 117 
hydrate, 162 
hypochlorite, 164 
iodate, 164 

iodide, 165 
iodo-hydrargyrate, 131 


98 
vi, crystals, frontispiece. 
vii, Spectroscopes, 216 


MAES, ‘earths, 221 
ene. ‘¢ absorption, 224 
ees ‘* blood, 226 


asbestus, 47 
black, 149 
chloride, 149 
potassium cyanide, 160 
sponge, 149 
Plugge’s reagent, 184, 144, 167 
Poirier’s blue, 88 


Potassium and its compounds, 150 


acetate, i51 

acid carbonate, 155 

acid chromate, 157 

acid pyroantimonate, 170 
acid sulphate, 173 
antimonous tartrate, 17 
bicarbonate, 155 
bichromate, 157 
bisulphate, 173 

bromate, 152 


vili, spectra, alk. metals, 220 
= oe 


xii, ‘* absorption, 227 


met-antimonate, 170 
nitrate, 166 
nitrite, 167 
nitro-prusside, 168 
oxalate, 168 
permanganate, 168, 15 
platino-cyanide, 160 
pyro-antimonate, 170 
rhodanate, 174 
silver cyanide, 160 
spectrum, 220 
stannous chloride, 171 
sulphate, 171 
sulphate, 172 
sulphide, 173 
sulpho-carbonate, 173 
sulpho-cyanate, 174 
sulpho-cyanide, 174 
tartrate, antimonous, 174 
tetroxalate, 168 
thio-cyanate, 174 
Prollius’ mixture, 71, 103 
Propeny] alcohol, 28, 106 
Pyrogallic acid, 18 
Pyrogallol, 18 
Pyrognostic reagents, 47 


254 


Pyrosulphurice acid, 105, 200 


Q 


Quarz, 174 

Quicksilver, 128 
R 

Raw flux, 104 - 


Red lead, 123 
Red wine spectrum, 227 
Resorcin, 175 
Resorcin yellow, 89 
Rochelle salt, 196 
Rohrbach’s solution, 52 
Rosaniline hydrochlorate, 80 
spectrum, 227 
Rosolic acid, 19, 175 
Rubidium spectrum, 220 
Ruthenium chloride, 176 


S 


Saccharin, test for, 175 
Sachse’s solution, 132 
Safranine hydrochlorate, 176 
spectrum, 225 
Sal ammoniac, 32 
Salicylic acid, 19 
Schaffgot’s solution, 32 
Scheibler’s reagent, 18 
Schlippe’s salt, 194 
Schmiedeberg’s solution, 99 
Schulze’s reagent, 17 
Seignette salt, 196 
Silicie acid, 19 
Silico-tungstic acid, 19 
Silk, test for, 210 
Silver and its compounds, 177 
nitrate, 178 
nitrite, 179 
oxide, 179 
potassium cyanide, 160 
sulphate, 179 
Skin powder, 180 
Soap solution, 180 


INDEX. 


Sodio-cobaltic nitrite, 75 

Sodium and its compounds, 181 
acetate, 182 
acid carbonate, 184 
acid sulphate, 195 
acid sulphite, 196 
acid tartrate, 196 
acid tungstate, 197 
amalgam, 182 
ammonium phosphate, 193 
arsenate, 183 
biborate, 186 
bicarbonate, 184 
bisulphate, 195 
bitartrate, 196 
bromate, 183 
carbonate, 183 
chloride, 185 
cobaltic nitrite, 75 
diborate, 186 
dicarbonate, 184 
disulphate, 195 
ditartrate, 196 
hydrate, 187 
hydrosulphite, 189 
hypobromite, 187 
hypochlorite, 187 
hyposulphite, 189 
iodate, 190 
meta-tungstate, 197 
molybdate, 190 
nitrate, 190 
nitrite, 191 
nitroprusside, 191 
oxalate, 192 
phosphate, 192 
phospho-molybdate, 12 
potassium tartrate, 196 
pyrophosphate, 193 
salicylate, 88, 194 
selenate, 194 
spectrum, 220 
sulphantimonate, 194 


Faisst and Knauss’ table, 181 sulphate, 195 


INDEX. 


sulphide, 195 — 
sulphite, 195 
tartrate, 196 
tungstate, 197 
wolframate, 197 
Soldaini’s reagent, 93 
Sonnenschein’s reagent, 12, 67 
Spectroscope, use of, 216 
Spirit of wine, 26 
Spiritus ammoniz, 31 
Stannic chloride, 203, 19 
Stannous chloride, 203 
caesium chloride, 203 
potassium chloride, 171 
potassium sulphate, 171 
Starch, 23, 110, 162, 197 
Strontium chloride, 198 
spectrum, 221 
sulphate, 199 
Strychnine, 6, 16 
Sugar, 200 
Sulphanilic acid, 20 
Sulph-indigotic acid, 82 
Sulpho-azobenzol-alpha-naphthol 
89 
beta-naphthol, 89 
Sulpho-dimethyl- amido - azoben- 
zol, 21, 78 
Sulpho-molybdic acid, 12 
Sulphur, 200 
dioxide, 23 
iodide, 200 
trioxide, 105, 200 
Sulphuric acid, 21 
anhydride, 200 
fuming, 105 
Sulphurous acid, 23 


T 


Tannic acid, 23 
Tannin, 23 

Tannin reactive, 182 
Tartar emetic, 174 
Tartaric acid, 24 


255 


Testpapers, 88 
Tetra-hydro-ellagic acid, 89 
Tetra methyl - para - phenylene- 
diamine, 43, 90 
Thallium nitrate, 201 
paper, 202 
spectrum, 221 
Thymol, 202 
Tin and its compounds, 202 
spectrum, 2 
stannic chloride, 203 
stannous chloride, 203 
potassium chloride, 171 
potassium sulphate, 171 
Titanic acid, 24 
Trichloracetic aldehyde, 25, 69 
acid, 25 
Tri-ethyl-phosphino, 204 
Tri-methyl-amine, 204 
Tri-nitrophenol, 18, 205 
Tropzolin, 78, 89 
Turmeric, 89 


U 


Uranium compounds, 205 
acetate, 205 
nitrate, 206 

Urea, 206 
spectrum, 225 

Uric acid, 14, 28 


Vv 


Vanadic acid, 35 
Vanillin, 87, 90, 207 


Ww 


Water, 207 
hardness of, 181 
organic matter in, 169 
Wenzel’s reagent, 169 
White flux, 104 
Wine, red, spectrum, 227 
color adulterations, 71 
Woodpulp, 42, 144, 162 


256 INDEX. 


Woodspirit, 27 Z 
Wurster’s papers, 43, 90 : Zine and its compounds, 208 
Wurster’s test for hydrogen diox- 

‘de. 218 amalgam, 209, 210 

ye chloride, 210 

ue Xx iodide, 210 
Xylidine, 208 sulphate, 211 
Y sulph-hydrate, 212 


Yeast, 208 


JOHN L. BOLAND 
BOOK AND PUBLISHING CO. 


Nos. 610 AND 612 WASHINGTON AVENUE, 


Sue, SMOUMposy ney 


Have just published : 


Lessons in Qualitative and Volumetric Chemical 
Analysis, for the use of ine (cians: pharmacists and 
students. By CHAS. 0. CURTMAN, Professor of Chemistry 
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Qualitative Chemical Analysis, arranged on the basis of the 
last German edition. Third edition, illustrated, 8 vo., pp, 
200 and XII. Cloth, $1.50. 


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Uses, Tests for Purity and Preparation of Chemical 
Reagents employed in Qualitative, Quantitative, Volume- 
trie, Docimastic, Microscopic and Petrographic Analysis, 
with a chapter on the use of the Spectroscope. 8 vo., pp. 
206. Price, Leather, $2.25 ; Cloth, $1.76, 















































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